Predict Collision Motion
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Middle School Physical Science › Predict Collision Motion
Two identical bumper cars (same mass) move on a flat surface. Car A moves east at $5,\text{m/s}$. Car B is at rest. Car A hits Car B from behind.
What is the best qualitative prediction for the motion of both cars right after the collision?
Neither car changes speed because equal masses make the collision forces cancel out.
Car A will slow down a lot (possibly stop) and Car B will move east; both change motion because the cars push on each other with equal and opposite forces.
Only Car B moves because it receives the force; Car A keeps $5,\text{m/s}$ because it is the one applying the force.
Both cars move west because the equal and opposite forces cancel the eastward motion.
Explanation
This question tests understanding of how Newton's Third Law allows us to predict that both objects in a collision will experience forces and change their motion. When two objects collide or interact, Newton's Third Law guarantees that both objects experience equal magnitude forces in opposite directions—this means both objects will change their motion during the interaction (both accelerate, though possibly in different amounts depending on their masses). When Car A (moving east at 5 m/s) collides with Car B (at rest), both cars experience equal magnitude forces during the collision: Car A experiences force to the west (opposite its motion) causing it to slow down significantly or stop, while Car B experiences equal force to the east causing it to accelerate from rest. Since the cars are identical (same mass), we predict Car A will slow down dramatically (possibly stop completely) while Car B speeds up to move east—a classic momentum transfer scenario where both motion states change. Choice A is correct because it properly predicts both objects change motion (Car A slows/stops, Car B moves east) based on both experiencing equal opposite forces during the collision. Choice B incorrectly claims only one car changes motion, violating Newton's Third Law; Choice C predicts both move west which is impossible when Car B starts at rest and receives eastward force; Choice D suggests no speed changes when collision forces must cause accelerations. For identical masses with one moving: the moving object typically transfers most or all of its motion to the stationary object—like billiard balls where the cue ball stops and the target ball moves away with the cue ball's original speed, demonstrating perfect momentum transfer while both objects experience equal forces and change their motion states.
Cart A (mass 1 kg) moves right at 3 m/s toward Cart B (mass 3 kg) that is at rest on a low-friction track. They collide and bounce apart (they do not stick).
During the collision, the carts exert equal and opposite forces on each other.
Which prediction is most reasonable for the motion changes of BOTH carts right after the collision?
Both carts change motion: Cart A is likely to slow down a lot or even bounce left, while Cart B starts moving right but more slowly than Cart A was moving.
Cart B stays at rest because it is heavier; only Cart A changes motion.
Cart A does not change motion because it was the one doing the pushing; Cart B moves right due to Cart A’s force.
Both carts change motion by the same amount because the forces are equal, so they must end with the same speed.
Explanation
This question tests understanding of how Newton's Third Law allows us to predict that both objects in a collision will experience forces and change their motion. When two objects collide or interact, Newton's Third Law guarantees that both objects experience equal magnitude forces in opposite directions—this means both objects will change their motion during the interaction (both accelerate, though possibly in different amounts depending on their masses); you cannot have a collision where only one object is affected; if Object A exerts force on Object B (changing B's motion), then Object B must exert an equal opposite force on Object A (changing A's motion as well)—both must change motion because both experience forces, though how much they change depends on F = ma with their respective masses. For unequal masses where a light cart (1 kg) collides with a heavy cart (3 kg) and they bounce apart, both experience equal forces during collision (Newton's Third Law), but F = ma predicts different motion changes: the light Cart A (small mass) undergoes large acceleration and bounces back dramatically to the left, while the heavy Cart B (large mass) undergoes small acceleration and moves right slowly. Choice B is correct because it properly predicts both objects change motion based on both experiencing forces and appropriately connects equal forces with different motion changes when masses differ, with Cart A slowing a lot or bouncing left and Cart B moving right slowly. Choice A is wrong because it predicts only one object changes motion, violating Newton's Third Law which requires both objects experience forces and thus both accelerate, and claims the heavier object remains completely unaffected when actually it experiences equal force and must accelerate (even if slightly). Predicting collision outcomes using Newton's Third Law: (1) recognize both objects will experience forces (equal magnitude, opposite directions), (2) apply F = ma to each object separately to predict acceleration directions (object experiencing force opposing its motion will slow or reverse; object experiencing force in its motion direction will speed up), (3) consider mass differences (same force on light object → large acceleration; same force on heavy object → small acceleration), (4) predict qualitatively (both change motion, but how much depends on mass), and (5) remember both are always affected even if one change is subtle. Common collision patterns: equal mass, one moving: roughly exchange velocities (moving stops, stationary moves); equal mass, both moving toward: both bounce back; unequal mass, light hits heavy: light bounces back, heavy continues mostly unchanged; person pushes massive object: person moves back, object barely moves (both experienced equal forces)—in all cases, both objects change motion because both experience forces, with the magnitude of change determined by F = ma for each object's mass.
Cart A (mass 2 kg) is moving right at 4 m/s on a low-friction track. Cart B (mass 2 kg) is at rest. They collide and stick together.
Before: A moving right, B at rest.
During: each cart pushes on the other with equal and opposite forces.
After: Which statement best predicts the motion of BOTH carts after the collision, and why both are affected?
Only Cart B changes motion because Cart A was already moving; Cart A keeps moving right at 4 m/s.
Both carts feel equal and opposite forces, so both change motion; they move together to the right at a speed less than 4 m/s.
Cart A exerts a larger force on Cart B than Cart B exerts on Cart A, so Cart B moves right while Cart A keeps the same speed.
Both carts feel forces, but Cart B stays at rest because it started at rest; Cart A slows down a little.
Explanation
This question tests understanding of how Newton's Third Law allows us to predict that both objects in a collision will experience forces and change their motion. When two objects collide or interact, Newton's Third Law guarantees that both objects experience equal magnitude forces in opposite directions—this means both objects will change their motion during the interaction (both accelerate, though possibly in different amounts depending on their masses); you cannot have a collision where only one object is affected; if Object A exerts force on Object B (changing B's motion), then Object B must exert an equal opposite force on Object A (changing A's motion as well)—both must change motion because both experience forces, though how much they change depends on F = ma with their respective masses. When Cart A (moving right at 4 m/s) collides with Cart B (at rest) and they stick together, both carts experience equal magnitude forces during the collision: Cart A experiences force to the left (opposite its motion) causing it to slow down, while Cart B experiences equal force to the right causing it to speed up from rest; since the carts have equal masses and stick, Cart A slows from 4 m/s to 2 m/s, and Cart B speeds up from 0 to 2 m/s, with both moving together right at 2 m/s after (momentum conservation). Choice B is correct because it properly predicts both objects change motion based on both experiencing forces and accurately describes them moving together to the right at a speed less than 4 m/s. Choice A is wrong because it predicts only Cart B changes motion, violating Newton's Third Law which requires both objects experience forces and thus both accelerate. Predicting collision outcomes using Newton's Third Law: (1) recognize both objects will experience forces (equal magnitude, opposite directions), (2) apply F = ma to each object separately to predict acceleration directions (object experiencing force opposing its motion will slow or reverse; object experiencing force in its motion direction will speed up), (3) consider mass differences (same force on light object → large acceleration; same force on heavy object → small acceleration), (4) predict qualitatively (both change motion, but how much depends on mass), and (5) remember both are always affected even if one change is subtle. Common collision patterns: equal mass, one moving: roughly exchange velocities (moving stops, stationary moves); equal mass, both moving toward: both bounce back; unequal mass, light hits heavy: light bounces back, heavy continues mostly unchanged; person pushes massive object: person moves back, object barely moves (both experienced equal forces)—in all cases, both objects change motion because both experience forces, with the magnitude of change determined by F = ma for each object's mass.
Two carts collide head-on on a low-friction track.
Before: Cart A (2 kg) moves right at 2 m/s. Cart B (2 kg) moves left at 2 m/s.
During: each cart exerts an equal and opposite force on the other.
After the collision, which statement best describes what can happen to BOTH carts’ motions?
Both carts must keep moving in their original directions because the forces are equal and cancel out.
Both carts change motion during the collision; they may slow down and could reverse directions depending on the details of the collision.
Cart A exerts more force because it is labeled A, so Cart B must reverse direction while Cart A keeps the same speed.
Only the cart moving right changes motion; the cart moving left is unaffected because it was “pushing back.”
Explanation
This question tests understanding of how Newton's Third Law allows us to predict that both objects in a collision will experience forces and change their motion. When two objects collide or interact, Newton's Third Law guarantees that both objects experience equal magnitude forces in opposite directions—this means both objects will change their motion during the interaction (both accelerate, though possibly in different amounts depending on their masses); you cannot have a collision where only one object is affected; if Object A exerts force on Object B (changing B's motion), then Object B must exert an equal opposite force on Object A (changing A's motion as well)—both must change motion because both experience forces, though how much they change depends on F = ma with their respective masses. When two equal-mass carts approach each other head-on at equal speeds and collide, both experience equal opposite forces, so both will change motion: they may slow down, stop, or reverse directions depending on whether the collision is elastic (reverse) or inelastic (stop or slow). Choice C is correct because it properly predicts both objects change motion based on both experiencing forces and accurately predicts they may slow down and could reverse directions from the opposite accelerations. Choice A is wrong because it predicts no motion change for either object, when collision forces must cause accelerations by F = ma, and claims forces cancel out overall but ignores that forces act on different objects. Predicting collision outcomes using Newton's Third Law: (1) recognize both objects will experience forces (equal magnitude, opposite directions), (2) apply F = ma to each object separately to predict acceleration directions (object experiencing force opposing its motion will slow or reverse; object experiencing force in its motion direction will speed up), (3) consider mass differences (same force on light object → large acceleration; same force on heavy object → small acceleration), (4) predict qualitatively (both change motion, but how much depends on mass), and (5) remember both are always affected even if one change is subtle. Common collision patterns: equal mass, one moving: roughly exchange velocities (moving stops, stationary moves); equal mass, both moving toward: both bounce back; unequal mass, light hits heavy: light bounces back, heavy continues mostly unchanged; person pushes massive object: person moves back, object barely moves (both experienced equal forces)—in all cases, both objects change motion because both experience forces, with the magnitude of change determined by F = ma for each object's mass.
A rocket in space fires its engine and shoots hot gases backward (to the left).
Before: rocket and gases are together.
During: rocket pushes gases left; gases push rocket right with equal and opposite force.
Which prediction best describes the motion changes of BOTH the rocket and the gases?
Both the rocket and the gases accelerate to the right because the rocket engine points right.
Only the gases accelerate because they are being pushed; the rocket stays at the same speed.
The rocket accelerates right while the gases accelerate left; both change motion due to equal and opposite forces.
The rocket accelerates right because it exerts a larger force on the gases than the gases exert on it.
Explanation
This question tests understanding of how Newton's Third Law allows us to predict that both objects in a collision will experience forces and change their motion. When two objects collide or interact, Newton's Third Law guarantees that both objects experience equal magnitude forces in opposite directions—this means both objects will change their motion during the interaction (both accelerate, though possibly in different amounts depending on their masses); you cannot have a collision where only one object is affected; if Object A exerts force on Object B (changing B's motion), then Object B must exert an equal opposite force on Object A (changing A's motion as well)—both must change motion because both experience forces, though how much they change depends on F = ma with their respective masses. In a rocket propulsion scenario where the rocket pushes gases left, both experience equal opposite forces: the gases accelerate left, and the rocket accelerates right; both change motion in opposite directions due to the interaction. Choice B is correct because it properly predicts both objects change motion based on both experiencing forces and accurately predicts direction of motion changes (opposite accelerations from opposite forces), with the rocket right and gases left. Choice A is wrong because it predicts only one object changes motion, violating Newton's Third Law which requires both objects experience forces and thus both accelerate, claiming the rocket stays unchanged when actually the gases push it equally. Predicting collision outcomes using Newton's Third Law: (1) recognize both objects will experience forces (equal magnitude, opposite directions), (2) apply F = ma to each object separately to predict acceleration directions (object experiencing force opposing its motion will slow or reverse; object experiencing force in its motion direction will speed up), (3) consider mass differences (same force on light object → large acceleration; same force on heavy object → small acceleration), (4) predict qualitatively (both change motion, but how much depends on mass), and (5) remember both are always affected even if one change is subtle. Common collision patterns: equal mass, one moving: roughly exchange velocities (moving stops, stationary moves); equal mass, both moving toward: both bounce back; unequal mass, light hits heavy: light bounces back, heavy continues mostly unchanged; person pushes massive object: person moves back, object barely moves (both experienced equal forces)—in all cases, both objects change motion because both experience forces, with the magnitude of change determined by F = ma for each object's mass.
Two ice skaters start at rest on smooth ice and push off each other.
Skater A has mass 50 kg. Skater B has mass 100 kg.
During the push, they exert equal and opposite forces on each other for the same time.
Which prediction best compares their motion right after they push apart?
They move in opposite directions; the 100 kg skater has a larger speed because heavier objects always move faster after a push.
They both remain at rest because the forces are equal and cancel.
They move in opposite directions; the 50 kg skater has a larger speed because the same force causes a larger acceleration for the smaller mass ($F=ma$).
They move in the same direction because the forces are equal.
Explanation
This question tests understanding of how Newton's Third Law allows us to predict that both objects in a collision will experience forces and change their motion. When two objects collide or interact, Newton's Third Law guarantees that both objects experience equal magnitude forces in opposite directions—this means both objects will change their motion during the interaction (both accelerate, though possibly in different amounts depending on their masses); you cannot have a collision where only one object is affected; if Object A exerts force on Object B (changing B's motion), then Object B must exert an equal opposite force on Object A (changing A's motion as well)—both must change motion because both experience forces, though how much they change depends on F = ma with their respective masses. For push-apart scenarios like two ice skaters pushing off from rest with unequal masses, both experience equal opposite forces (Newton's Third Law), so both accelerate away in opposite directions; the lighter 50 kg skater moves faster than the heavier 100 kg skater because F = ma gives larger acceleration for smaller mass (same F, smaller m → larger a), yet both are affected and both move. Choice C is correct because it correctly applies Newton's Third Law to conclude both objects affected and appropriately connects equal forces with different motion changes when masses differ, predicting opposite directions with the lighter having larger speed. Choice D is wrong because it bases prediction on mass only without considering forces, claiming heavier always moves faster, missing that forces are equal and both objects must respond but with accelerations inversely proportional to mass. Predicting collision outcomes using Newton's Third Law: (1) recognize both objects will experience forces (equal magnitude, opposite directions), (2) apply F = ma to each object separately to predict acceleration directions (object experiencing force opposing its motion will slow or reverse; object experiencing force in its motion direction will speed up), (3) consider mass differences (same force on light object → large acceleration; same force on heavy object → small acceleration), (4) predict qualitatively (both change motion, but how much depends on mass), and (5) remember both are always affected even if one change is subtle. Common collision patterns: equal mass, one moving: roughly exchange velocities (moving stops, stationary moves); equal mass, both moving toward: both bounce back; unequal mass, light hits heavy: light bounces back, heavy continues mostly unchanged; person pushes massive object: person moves back, object barely moves (both experienced equal forces)—in all cases, both objects change motion because both experience forces, with the magnitude of change determined by F = ma for each object's mass.
A moving bowling ball rolls into a stationary bowling pin.
Before: ball moving forward; pin at rest.
During: the ball pushes on the pin, and the pin pushes back on the ball with an equal and opposite force.
Which statement best explains why BOTH objects’ motions change during the collision?
Only the pin changes motion because it is lighter; the ball feels no force from the pin.
Both change motion because each exerts a force on the other; the forces are equal and opposite (Newton’s Third Law), so each can accelerate (Newton’s Second Law).
The pin changes motion because the ball exerts a force, but the ball cannot change motion because it was already moving.
Both change motion because the ball’s force is larger than the pin’s force, so the pin moves more.
Explanation
This question tests understanding of how Newton's Third Law allows us to predict that both objects in a collision will experience forces and change their motion. When two objects collide or interact, Newton's Third Law guarantees that both objects experience equal magnitude forces in opposite directions—this means both objects will change their motion during the interaction (both accelerate, though possibly in different amounts depending on their masses); you cannot have a collision where only one object is affected; if Object A exerts force on Object B (changing B's motion), then Object B must exert an equal opposite force on Object A (changing A's motion as well)—both must change motion because both experience forces, though how much they change depends on F = ma with their respective masses. When a heavy bowling ball hits a light stationary pin, both experience equal opposite forces (Newton's Third Law), causing both to accelerate (Newton's Second Law): the ball slows slightly, and the pin speeds up dramatically forward. Choice B is correct because it correctly applies Newton's Third Law to conclude both objects affected, explaining both change motion due to equal opposite forces leading to accelerations. Choice A is wrong because it predicts only one object changes motion, violating Newton's Third Law which requires both objects experience forces and thus both accelerate, and claims the ball feels no force when actually the pin pushes back equally. Predicting collision outcomes using Newton's Third Law: (1) recognize both objects will experience forces (equal magnitude, opposite directions), (2) apply F = ma to each object separately to predict acceleration directions (object experiencing force opposing its motion will slow or reverse; object experiencing force in its motion direction will speed up), (3) consider mass differences (same force on light object → large acceleration; same force on heavy object → small acceleration), (4) predict qualitatively (both change motion, but how much depends on mass), and (5) remember both are always affected even if one change is subtle. Common collision patterns: equal mass, one moving: roughly exchange velocities (moving stops, stationary moves); equal mass, both moving toward: both bounce back; unequal mass, light hits heavy: light bounces back, heavy continues mostly unchanged; person pushes massive object: person moves back, object barely moves (both experienced equal forces)—in all cases, both objects change motion because both experience forces, with the magnitude of change determined by F = ma for each object's mass.
Cart A (mass 4 kg) moves right at 2 m/s toward Cart B (mass 1 kg) that is at rest. They collide.
During the collision, the force on A from B and the force on B from A are equal in size and opposite in direction.
Which object has the greater acceleration (bigger change in motion per second) during the collision, and why?
Cart A, because the heavier object always has the greater acceleration in a collision.
They have the same acceleration because the forces are equal, so $a$ must be equal too.
Cart B, because the same force causes a larger acceleration for the smaller mass ($a=F/m$), even though both forces are equal and opposite.
Neither cart accelerates because the forces are equal and cancel out between the carts.
Explanation
This question tests understanding of how Newton's Third Law allows us to predict that both objects in a collision will experience forces and change their motion. When two objects collide or interact, Newton's Third Law guarantees that both objects experience equal magnitude forces in opposite directions—this means both objects will change their motion during the interaction (both accelerate, though possibly in different amounts depending on their masses); you cannot have a collision where only one object is affected; if Object A exerts force on Object B (changing B's motion), then Object B must exert an equal opposite force on Object A (changing A's motion as well)—both must change motion because both experience forces, though how much they change depends on F = ma with their respective masses. For unequal masses where heavy Cart A (4 kg) hits light Cart B (1 kg), both experience equal forces, but the light Cart B undergoes larger acceleration (a = F/m, smaller m → larger a) and thus bigger motion change per second. Choice B is correct because it appropriately connects equal forces with different motion changes when masses differ, explaining the smaller mass has greater acceleration even though forces are equal and opposite. Choice C is wrong because it claims both objects show identical motion changes ignoring that F = ma means different masses produce different accelerations for the same force. Predicting collision outcomes using Newton's Third Law: (1) recognize both objects will experience forces (equal magnitude, opposite directions), (2) apply F = ma to each object separately to predict acceleration directions (object experiencing force opposing its motion will slow or reverse; object experiencing force in its motion direction will speed up), (3) consider mass differences (same force on light object → large acceleration; same force on heavy object → small acceleration), (4) predict qualitatively (both change motion, but how much depends on mass), and (5) remember both are always affected even if one change is subtle. Common collision patterns: equal mass, one moving: roughly exchange velocities (moving stops, stationary moves); equal mass, both moving toward: both bounce back; unequal mass, light hits heavy: light bounces back, heavy continues mostly unchanged; person pushes massive object: person moves back, object barely moves (both experienced equal forces)—in all cases, both objects change motion because both experience forces, with the magnitude of change determined by F = ma for each object's mass.
Two carts on a low-friction track are connected by a compressed spring between them. They start at rest, then the spring is released and pushes them apart. Cart A has mass $1,\text{kg}$ and Cart B has mass $4,\text{kg}$.
Which prediction is most accurate about their motions right after release?
Both carts move in the same direction because the spring pushes them forward together.
Cart B moves faster because the larger mass means the spring force on it is larger.
Cart A and Cart B move in opposite directions; Cart A ends up with the larger speed because both experience equal and opposite forces but Cart A has the smaller mass ($a=F/m$).
Only Cart A moves because the spring is closer to Cart A, so Cart A gets all the force.
Explanation
This question tests understanding of how Newton's Third Law allows us to predict that both objects in a collision will experience forces and change their motion. When two objects collide or interact, Newton's Third Law guarantees that both objects experience equal magnitude forces in opposite directions—this means both objects will change their motion during the interaction (both accelerate, though possibly in different amounts depending on their masses). You cannot have a collision where only one object is affected; if Object A exerts force on Object B (changing B's motion), then Object B must exert an equal opposite force on Object A (changing A's motion as well)—both must change motion because both experience forces, though how much they change depends on F = ma with their respective masses. For push-apart: Two ice skaters push off each other from rest—both experience equal opposite forces (Newton's Third Law), so both accelerate away from each other in opposite directions. If they have equal masses, they move with equal speeds (one left, one right), but if one skater is heavier, the lighter skater moves faster and the heavier moves slower (F = ma: same F, smaller m gives larger a), yet both are affected and both move because both experienced forces. Choice A is correct because it properly predicts both objects change motion based on both experiencing forces / correctly applies Newton's Third Law to conclude both objects affected / accurately predicts direction of motion changes (opposite accelerations from opposite forces) / appropriately connects equal forces with different motion changes when masses differ. Choice B is wrong because it predicts only one object changes motion, violating Newton's Third Law which requires both objects experience forces and thus both accelerate / claims both objects show identical motion changes ignoring that F = ma means different masses produce different accelerations for the same force / predicts motion changes in the same direction when the opposite forces should produce opposite accelerations / suggests the stationary or heavier object remains completely unaffected, when actually it experiences equal force and must accelerate (even if imperceptibly). Predicting collision outcomes using Newton's Third Law: (1) recognize both objects will experience forces (equal magnitude, opposite directions), (2) apply F = ma to each object separately to predict acceleration directions (object experiencing force opposing its motion will slow or reverse; object experiencing force in its motion direction will speed up), (3) consider mass differences (same force on light object → large acceleration; same force on heavy object → small acceleration), (4) predict qualitatively (both change motion, but how much depends on mass), and (5) remember both are always affected even if one change is subtle (wall moves infinitesimally when person pushes, but it does experience force and technically accelerates). Common collision patterns: equal mass, one moving: roughly exchange velocities (moving stops, stationary moves); equal mass, both moving toward: both bounce back; unequal mass, light hits heavy: light bounces back, heavy continues mostly unchanged; person pushes massive object: person moves back, object barely moves (both experienced equal forces)—in all cases, both objects change motion because both experience forces, with the magnitude of change determined by F = ma for each object's mass.
Two ice skaters start at rest on frictionless ice. Skater A has mass $50,\text{kg}$ and Skater B has mass $100,\text{kg}$. They push off each other and separate.
Which prediction best describes what happens immediately after they push, and why?
Skater B moves faster because the heavier skater produces a larger force.
Only Skater A moves because Skater A is the one who decided to push first.
Skater A moves faster than Skater B; they push with equal and opposite forces, but the smaller mass has the larger acceleration ($a=F/m$).
They both move away at the same speed because Newton’s Third Law means they must have the same acceleration.
Explanation
This question tests understanding of how Newton's Third Law allows us to predict that both objects in a collision will experience forces and change their motion. When two objects collide or interact, Newton's Third Law guarantees that both objects experience equal magnitude forces in opposite directions—this means both objects will change their motion during the interaction (both accelerate, though possibly in different amounts depending on their masses). You cannot have a collision where only one object is affected; if Object A exerts force on Object B (changing B's motion), then Object B must exert an equal opposite force on Object A (changing A's motion as well)—both must change motion because both experience forces, though how much they change depends on F = ma with their respective masses. For push-apart: Two ice skaters push off each other from rest—both experience equal opposite forces (Newton's Third Law), so both accelerate away from each other in opposite directions. If they have equal masses, they move with equal speeds (one left, one right), but if one skater is heavier, the lighter skater moves faster and the heavier moves slower (F = ma: same F, smaller m gives larger a), yet both are affected and both move because both experienced forces. Choice B is correct because it properly predicts both objects change motion based on both experiencing forces / correctly applies Newton's Third Law to conclude both objects affected / accurately predicts direction of motion changes (opposite accelerations from opposite forces) / appropriately connects equal forces with different motion changes when masses differ. Choice A is wrong because it predicts only one object changes motion, violating Newton's Third Law which requires both objects experience forces and thus both accelerate / claims both objects show identical motion changes ignoring that F = ma means different masses produce different accelerations for the same force / predicts motion changes in the same direction when the opposite forces should produce opposite accelerations / suggests the stationary or heavier object remains completely unaffected, when actually it experiences equal force and must accelerate (even if imperceptibly). Predicting collision outcomes using Newton's Third Law: (1) recognize both objects will experience forces (equal magnitude, opposite directions), (2) apply F = ma to each object separately to predict acceleration directions (object experiencing force opposing its motion will slow or reverse; object experiencing force in its motion direction will speed up), (3) consider mass differences (same force on light object → large acceleration; same force on heavy object → small acceleration), (4) predict qualitatively (both change motion, but how much depends on mass), and (5) remember both are always affected even if one change is subtle (wall moves infinitesimally when person pushes, but it does experience force and technically accelerates). Common collision patterns: equal mass, one moving: roughly exchange velocities (moving stops, stationary moves); equal mass, both moving toward: both bounce back; unequal mass, light hits heavy: light bounces back, heavy continues mostly unchanged; person pushes massive object: person moves back, object barely moves (both experienced equal forces)—in all cases, both objects change motion because both experience forces, with the magnitude of change determined by F = ma for each object's mass.