AP Physics 1 Quiz: Elastic And Inelastic Collisions

What this quiz covers

This quiz focuses on Elastic And Inelastic Collisions, giving you a quick way to practice the rules, question types, and explanations that matter most for AP Physics 1.

How to use this quiz

Try each quiz question before looking at the correct answer. Use the explanations to review missed ideas, then come back to similar questions until the pattern feels familiar.

Question 1

1. The collision is elastic because the carts did not stick together.
2. Momentum is not conserved because kinetic energy decreased.
3. The collision is inelastic, but momentum of the system is still conserved. (correct answer)
4. Both momentum and kinetic energy are conserved since the track is horizontal.

Explanation: This question examines the distinction between elastic and inelastic collisions based on energy changes. Momentum conservation holds in isolated systems for all collisions, regardless of energy loss. In elastic collisions, kinetic energy is fully conserved alongside momentum. In inelastic collisions, momentum is conserved, but kinetic energy decreases, often due to deformation or sound. A common distractor is choice A, which assumes bouncing means elastic, but KE decrease confirms inelasticity. To solve collision problems, calculate or compare kinetic energy before and after to classify the type while always applying momentum conservation.

Question 2

1. It must be conserved because momentum is conserved.
2. It must decrease because the collision is perfectly inelastic. (correct answer)
3. It must increase because the carts combine masses.
4. It becomes zero because the carts stick together.

Explanation: This question probes the behavior of kinetic energy in elastic versus inelastic collisions. Momentum is conserved in all isolated collisions without external forces. Elastic collisions maintain both momentum and total kinetic energy. Inelastic collisions, especially perfectly inelastic ones where objects merge, conserve momentum but result in kinetic energy loss. Choice A is a distractor, incorrectly linking KE conservation directly to momentum without considering collision type. A transferable strategy is to recognize sticking as a sign of perfectly inelastic collisions and expect KE reduction accordingly.

Question 3

1. The collision is perfectly inelastic because the carts reverse direction.
2. The collision is elastic; both momentum and kinetic energy are conserved. (correct answer)
3. The collision is inelastic; momentum is not conserved because they bounce.
4. Kinetic energy is conserved in all collisions, so the collision type cannot be determined.

Explanation: This question tests understanding of elastic and inelastic collisions. When objects return to their original speeds after bouncing apart (just in opposite directions), both momentum and kinetic energy are conserved, indicating an elastic collision. In elastic collisions, objects exchange momentum and energy without permanent deformation or energy loss. The fact that they bounce back to original speeds is a classic signature of elastic behavior. Choice A incorrectly labels this as perfectly inelastic, which would require the carts to stick together. To identify elastic collisions, look for objects that bounce apart while maintaining the same total kinetic energy as before the collision.

Question 4

1. Both momentum and kinetic energy are conserved because the track is level.
2. Momentum is conserved, but kinetic energy is not conserved because the carts stick together. (correct answer)
3. Kinetic energy is conserved, but momentum is not conserved because the carts stick together.
4. Neither momentum nor kinetic energy is conserved because the carts stick together.

Explanation: This question tests understanding of elastic and inelastic collisions. In all collisions between objects in an isolated system, momentum is conserved due to Newton's third law - the internal forces between objects are equal and opposite, so the total momentum remains constant. However, kinetic energy is only conserved in elastic collisions where objects bounce apart without permanent deformation. In this collision, the carts stick together, which is the defining characteristic of a perfectly inelastic collision where kinetic energy is lost to deformation, sound, and heat. Choice A incorrectly claims both are conserved, ignoring that sticking indicates energy loss. When objects stick together after collision, remember that momentum is still conserved but kinetic energy is always lost.

Question 5

1. The collision is elastic, so momentum is also conserved for the two-cart system. (correct answer)
2. The collision must be perfectly inelastic.
3. Momentum is not conserved because energy data were used.
4. Kinetic energy equality implies the final momentum is zero.

Explanation: This question tests understanding of elastic and inelastic collisions. When measurements show that total kinetic energy before equals total kinetic energy after a collision, this defines an elastic collision. In elastic collisions, both momentum and kinetic energy are conserved for the system. This conservation occurs because no energy is lost to heat, sound, or permanent deformation. Choice B incorrectly suggests the collision must be perfectly inelastic—that would require the carts to stick together and lose kinetic energy. The strategy for identifying collision types: if kinetic energy is conserved, it's elastic and momentum is also conserved; if kinetic energy decreases, it's inelastic but momentum is still conserved.

Question 6

1. Whether the carts experience equal and opposite forces during the collision.
2. The carts’ velocities after the collision. (correct answer)
3. The carts’ masses before the collision.
4. Whether momentum is conserved during the collision.

Explanation: This question tests understanding of elastic and inelastic collisions. To determine whether a collision is elastic (kinetic energy conserved) or inelastic (kinetic energy not conserved), we need to compare the total kinetic energy before and after the collision. We already know the masses and initial velocities, so we can calculate the initial kinetic energy. However, to calculate the final kinetic energy, we need the final velocities of both carts after they bounce apart. Choice A incorrectly assumes rebounding guarantees elasticity, while choices C and D ask for information we already have or that's always true. The key strategy is to calculate kinetic energy using KE = ½mv² for each object before and after collision - if the totals match, it's elastic.

Question 7

1. Momentum is conserved only if the carts have equal mass.
2. Momentum is not conserved because the carts exert forces on each other.
3. Both momentum and kinetic energy are conserved. (correct answer)
4. Only kinetic energy is conserved in an elastic collision.

Explanation: This question evaluates the definition and implications of elastic collisions in AP Physics 1. Conservation of momentum applies to all isolated collisions, elastic or inelastic, due to balanced internal forces. Elastic collisions uniquely conserve kinetic energy as well, with total KE unchanged post-collision. Inelastic collisions do not conserve KE, even if objects separate. Choice D mistakenly states that only kinetic energy is conserved in elastic collisions, overlooking that momentum is also always conserved. A transferable strategy is to verify elasticity by confirming unchanged total KE and apply both conservation laws simultaneously for elastic problems.

Question 8

1. Total momentum is conserved, and total kinetic energy decreases. (correct answer)
2. Total kinetic energy is conserved, and total momentum decreases.
3. Both total momentum and total kinetic energy are conserved.
4. Total momentum becomes zero because the carts stick together.

Explanation: This question examines conservation principles in perfectly inelastic collisions in AP Physics 1. Momentum conservation holds in both elastic and inelastic collisions for isolated systems, ensuring the total momentum remains constant. Elastic collisions preserve kinetic energy, with no loss to other forms. Inelastic collisions, particularly perfectly inelastic ones where objects stick, result in kinetic energy decrease while momentum is conserved. Choice D erroneously states that momentum becomes zero when carts stick, but momentum is conserved and depends on initial conditions, not zero unless initially zero. A transferable strategy is to calculate post-collision velocity using momentum conservation and compare kinetic energies to confirm loss in inelastic cases.

Question 9

1. Kinetic energy must be conserved because the ball reverses direction.
2. Kinetic energy may or may not be conserved; more information is needed. (correct answer)
3. Kinetic energy cannot be conserved because momentum is always lost in collisions.
4. Kinetic energy must decrease because the cart was initially at rest.

Explanation: This question assesses uncertainty in kinetic energy conservation for collisions in AP Physics 1. Momentum is always conserved in isolated collisions, but kinetic energy conservation distinguishes elastic from inelastic types. In elastic collisions, both quantities are conserved, often with objects rebounding. In inelastic collisions, kinetic energy decreases, though rebounding can still occur depending on masses and velocities. Choice A wrongly claims kinetic energy must be conserved due to direction reversal, but reversal can happen in inelastic cases without KE conservation. A transferable strategy is to gather data on masses and velocities to calculate both momentum and KE before and after, determining the collision type empirically.

Question 10

1. Elastic, because kinetic energy is conserved in addition to momentum. (correct answer)
2. Perfectly inelastic, because one object stops after impact.
3. Inelastic, because momentum is not conserved in collisions.
4. Inelastic, because kinetic energy is always conserved in collisions.

Explanation: This question evaluates the distinction between elastic and inelastic collisions in AP Physics 1. In isolated systems, momentum is conserved in both elastic and inelastic collisions due to Newton's third law and no external forces. Elastic collisions conserve both momentum and kinetic energy, often resulting in objects bouncing apart with unchanged total KE. Inelastic collisions conserve momentum but not kinetic energy, with objects possibly sticking or separating but with energy loss. For instance, choice B wrongly labels it perfectly inelastic because one object stops, but perfectly inelastic requires sticking together, not separation. A transferable strategy is to check if initial and final kinetic energies match to confirm elasticity, especially for equal-mass head-on collisions where velocities exchange.

Question 11

1. Momentum is not conserved because both carts were moving before impact.
2. Kinetic energy is conserved because both carts move in the same direction.
3. Momentum is conserved, but kinetic energy is not conserved. (correct answer)
4. Both momentum and kinetic energy are not conserved because they stick.

Explanation: This question probes the application of conservation laws to inelastic collisions in AP Physics 1. In any collision without external forces, momentum is conserved for the system, reflecting the internal nature of interaction forces. Elastic collisions additionally conserve kinetic energy, keeping the total unchanged. Inelastic collisions conserve momentum but not kinetic energy, especially when objects stick together after colliding. Choice A incorrectly asserts that momentum is not conserved because both were moving, but conservation applies regardless of initial motions in isolated systems. A transferable strategy is to treat the system as isolated and use vector momentum for direction-dependent collisions, while checking for KE conservation separately.

Question 12

1. Momentum is conserved, and kinetic energy is conserved (elastic collision). (correct answer)
2. Momentum is not conserved because the balls separate after contact.
3. Kinetic energy is conserved in all collisions, so it must be conserved here.
4. Momentum is conserved only if the balls stick together.

Explanation: This question evaluates knowledge of elastic and inelastic collisions involving identical objects. Momentum is always conserved in isolated collisions with no external forces, such as on a low-friction surface. Elastic collisions conserve both momentum and kinetic energy, often resulting in objects bouncing apart with the same relative speeds. Inelastic collisions conserve momentum but not kinetic energy, and while objects can bounce apart, steel balls bouncing suggests an elastic nature here. A frequent distractor is choice B, which wrongly claims momentum is not conserved because the balls separate, ignoring that conservation applies regardless of separation. A useful strategy for collision problems is to assume momentum conservation first, then verify kinetic energy equality to classify as elastic or inelastic.

Question 13

1. The final momentum must be zero because the carts stick together.
2. The final momentum equals the initial total momentum (conserved). (correct answer)
3. The final momentum is greater than the initial momentum because mass increased.
4. Momentum is not conserved in perfectly inelastic collisions.

Explanation: This question evaluates momentum conservation in inelastic collisions. Total momentum remains conserved in isolated collisions, equaling initial momentum post-collision. In elastic collisions, KE is also conserved, but this is irrelevant here. Inelastic collisions with sticking conserve momentum but not KE, yet final momentum matches initial. Choice A distracts by suggesting final momentum is zero due to sticking, confusing it with equal opposite initial momenta. Always calculate total initial momentum and set it equal to final for conserved systems in collision problems.

Question 14

1. The collision is elastic because the carts move together afterward.
2. Momentum is not conserved because the collision is perfectly inelastic.
3. Kinetic energy is conserved because the final speed is nonzero.
4. The collision is perfectly inelastic, so kinetic energy is not conserved. (correct answer)

Explanation: This question tests understanding of elastic and inelastic collisions. When objects stick together after collision, it's called a perfectly inelastic collision, which means kinetic energy is definitely not conserved—some converts to other forms like heat or deformation. However, momentum is still conserved in this collision because external forces are negligible. The fact that the combined cart moves with nonzero speed doesn't mean kinetic energy is conserved; the final kinetic energy is less than the initial. Choice B incorrectly claims momentum isn't conserved in perfectly inelastic collisions—momentum is always conserved when external forces are negligible. The key insight: perfectly inelastic means objects stick together and kinetic energy decreases, but momentum is still conserved.

Question 15

1. Momentum is conserved, but kinetic energy is not conserved. (correct answer)
2. Kinetic energy is conserved, but momentum is not conserved.
3. Both momentum and kinetic energy are conserved because the carts are identical.
4. Objects sticking together implies the final momentum is zero.

Explanation: This question tests understanding of elastic and inelastic collisions. When two objects collide and stick together, this is a perfectly inelastic collision - the most inelastic type possible. In all collisions of isolated systems, momentum is conserved because the forces between objects are internal and cancel out according to Newton's third law. However, kinetic energy is not conserved in inelastic collisions; some energy is transformed into heat, sound, and permanent deformation as the objects merge. Choice C incorrectly assumes identical masses guarantee energy conservation, while choice D wrongly claims sticking implies zero final momentum. Remember that objects sticking together is the hallmark of a perfectly inelastic collision where maximum kinetic energy is lost while momentum remains conserved.

Question 16

1. Total kinetic energy, because external impulse is negligible.
2. Total momentum, even though kinetic energy decreases. (correct answer)
3. Neither momentum nor kinetic energy, because the carts stick.
4. Total momentum only if the carts have the same mass.

Explanation: This question tests understanding of elastic and inelastic collisions. On a horizontal air track with negligible external horizontal forces, momentum is always conserved for the system, regardless of collision type. When carts stick together, this is a perfectly inelastic collision where kinetic energy is not conserved—it decreases as some converts to other forms. The conservation of momentum doesn't depend on whether objects stick or their masses; it depends only on external forces being negligible. Choice C incorrectly claims momentum isn't conserved because carts stick—sticking affects kinetic energy conservation, not momentum conservation. Remember: momentum conservation depends on external forces, while sticking determines if the collision is perfectly inelastic with kinetic energy loss.

Question 17

1. Elastic collision: momentum and kinetic energy are conserved for the two-cart system. (correct answer)
2. Inelastic collision: momentum is not conserved because the carts separate.
3. Perfectly inelastic collision: kinetic energy is conserved because they bounce.
4. Collision type cannot be determined because kinetic energy is always conserved.

Explanation: This question tests understanding of elastic and inelastic collisions. When the system's total kinetic energy remains unchanged after a collision, this defines an elastic collision. In elastic collisions, both momentum and kinetic energy are conserved for the isolated system. The rubber ball cart likely has elastic properties that allow it to bounce without permanent deformation or energy loss. Choice C incorrectly calls this perfectly inelastic while claiming kinetic energy is conserved, but perfectly inelastic collisions always lose kinetic energy. To identify collision types, check kinetic energy: unchanged means elastic, decreased means inelastic, and maximum loss with sticking means perfectly inelastic.

Question 18

1. Because one cart rebounds, the collision must be elastic and kinetic energy is conserved.
2. Momentum is conserved, but kinetic energy is conserved only if the collision is elastic. (correct answer)
3. Momentum is not conserved because the carts change directions.
4. Kinetic energy is conserved in all collisions, so momentum must also be conserved.

Explanation: This question tests understanding of elastic and inelastic collisions. In any collision between isolated objects, momentum is always conserved due to Newton's third law - the forces between objects are equal and opposite, so total momentum remains constant regardless of whether objects stick or bounce. Kinetic energy conservation depends on the collision type: it's conserved only in elastic collisions where objects bounce without permanent deformation, but not in inelastic collisions where energy transforms to heat, sound, or deformation. The fact that Cart 1 rebounds doesn't guarantee the collision is elastic - it could still be inelastic if kinetic energy decreases. Choice C wrongly claims changing directions violates momentum conservation, confusing velocity direction with momentum magnitude. Always remember that momentum conservation is universal for isolated systems, while kinetic energy conservation requires elastic conditions.

Question 19

1. Perfectly inelastic, so momentum is not conserved.
2. Inelastic, because kinetic energy is always lost in collisions.
3. Elastic, so both momentum and kinetic energy are conserved. (correct answer)
4. Elastic, so momentum is not conserved but kinetic energy is conserved.

Explanation: This question tests understanding of elastic and inelastic collisions. In elastic collisions, both momentum and kinetic energy are conserved for the system. The problem states that total kinetic energy remains unchanged after the collision, which is the defining characteristic of an elastic collision. In inelastic collisions, kinetic energy is converted to other forms like heat or deformation, so total kinetic energy decreases. Choice B incorrectly claims kinetic energy is always lost in collisions, but elastic collisions preserve kinetic energy. To identify collision types, check if kinetic energy is conserved (elastic) or lost (inelastic), while momentum is conserved in both cases.

Question 20

1. The collision is inelastic; momentum of the two-glider system is still conserved. (correct answer)
2. The collision is elastic because the gliders did not stick.
3. Momentum is not conserved because kinetic energy decreased.
4. The final momentum must be zero since kinetic energy decreased.

Explanation: This question tests understanding of elastic and inelastic collisions. When total kinetic energy decreases after a collision, this defines an inelastic collision—some kinetic energy has converted to other forms like heat or sound. However, momentum is still conserved for the two-glider system because external forces are negligible. The fact that gliders separate doesn't make it elastic; what matters is that kinetic energy decreased. Choice C incorrectly claims momentum isn't conserved because kinetic energy decreased—these are independent conservation laws, and momentum is conserved regardless of energy changes when external forces are negligible. The key principle: inelastic means kinetic energy decreases, but momentum is still conserved in isolated systems.