Middle School Science Quiz: Balanced Vs Unbalanced Forces

What this quiz covers

This quiz focuses on Balanced Vs Unbalanced Forces, giving you a quick way to practice the rules, question types, and explanations that matter most for Middle School Science.

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. Situation 1 is unbalanced and the book accelerates upward; Situation 2 is balanced so it moves at constant speed.
2. Situation 1 is balanced with $F_{\text{net}}=0$ so there is no acceleration; Situation 2 is unbalanced with $F_{\text{net}}=5\,\text{N}$ to the right so the book accelerates right. (correct answer)
3. Situation 1 is balanced only if the book is moving; since it is at rest, the forces must be unbalanced.
4. Situation 2 is balanced because there are four forces acting, so the net force must be zero.

Question 2

1. Case 1 has $F_{\text{net}}=0$ so the car can move at constant velocity; Case 2 has $F_{\text{net}}=200\,\text{N}$ forward so the car accelerates forward. (correct answer)
2. Case 1 has $F_{\text{net}}=1000\,\text{N}$ forward so the car accelerates; Case 2 has $F_{\text{net}}=0$ so it is at rest.
3. Both cases are balanced because the car is moving, so neither case can involve acceleration.
4. Case 2 is balanced because there are more newtons forward, so the car's speed stays the same.

Question 3

1. Forces are balanced ($F_{\text{net}}=0$), so the skydiver falls at constant speed.
2. Forces are unbalanced with $F_{\text{net}}=700\,\text{N}$ downward, so the skydiver accelerates downward. (correct answer)
3. Forces are unbalanced with $F_{\text{net}}=900\,\text{N}$ downward, so the skydiver accelerates downward.
4. Forces are balanced because there are two forces, so the skydiver does not move.

Question 4

1. Forces are unbalanced ($F_{net}=20\text{ N}$ upward), so the book accelerates upward.
2. Forces are balanced ($F_{net}=0$), so the book has no acceleration and stays at rest. (correct answer)
3. Forces are balanced ($F_{net}=0$), so the book must be moving at constant speed across the table.
4. Forces are unbalanced because there are two forces, so the book accelerates downward.

Question 5

1. It speeds up because a force is applied to the right.
2. It slows down because friction always makes objects stop, even if forces balance.
3. It continues at constant velocity because $F_{net}=0$ (balanced forces). (correct answer)
4. It accelerates to the left because friction is present.

Question 6

1. Forces are balanced ($F_{net}=0$), so the skydiver falls at constant speed.
2. Forces are unbalanced ($F_{net}$ downward), so the skydiver accelerates downward (speeds up). (correct answer)
3. Forces are unbalanced ($F_{net}$ upward), so the skydiver accelerates upward.
4. Forces are balanced because gravity is always present, so there is no acceleration.

Question 7

1. The forces are unbalanced, so the cart must be speeding up to the right.
2. The net force is $8\,\text{N}$ to the right, so the cart keeps a constant speed.
3. The forces are balanced ($F_{\text{net}}=0$), so the cart has no acceleration and can move at constant velocity. (correct answer)
4. Balanced forces mean the cart must be at rest, not moving.

Question 8

1. Forces are balanced because there are two teams; the rope stays at rest.
2. $F_{net}=20\text{ N}$ to the left, so the rope accelerates to the left. (correct answer)
3. $F_{net}=100\text{ N}$ to the left, so the rope accelerates to the left.
4. $F_{net}=0\text{ N}$, so the rope accelerates to the left.

Question 9

1. $F_{net}=25\text{ N}$ to the right, so it moves at constant velocity to the right.
2. $F_{net}=5\text{ N}$ to the right, so it accelerates to the right. (correct answer)
3. $F_{net}=0\text{ N}$, so it accelerates to the right.
4. $F_{net}=5\text{ N}$ to the left, so it accelerates to the left.

Question 10

1. $F_{net}=20\text{ N}$ to the left; the rope accelerates to the left. (correct answer)
2. $F_{net}=120\text{ N}$ to the left; the rope accelerates to the left.
3. $F_{net}=0$; the rope stays at rest because forces act in opposite directions.
4. $F_{net}=20\text{ N}$ to the right; the rope accelerates to the right.

Question 11

1. Situation 1: unbalanced, stays at rest; Situation 2: balanced, accelerates right.
2. Situation 1: balanced, stays at rest; Situation 2: unbalanced, accelerates right. (correct answer)
3. Situation 1: balanced, accelerates left; Situation 2: unbalanced, moves at constant speed right.
4. Situation 1: unbalanced, accelerates right; Situation 2: balanced, stays at rest.

Question 12

1. The forces are unbalanced ($F_{\text{net}}=20\,\text{N}$ downward), so the book accelerates downward.
2. The forces are balanced ($F_{\text{net}}=0$), so the book has no acceleration and stays at rest. (correct answer)
3. The forces are unbalanced ($F_{\text{net}}=10\,\text{N}$ upward), so the book accelerates upward.
4. The forces are balanced, so the book must move upward at a constant speed.

Question 13

1. Situation 1 is balanced and Situation 2 is unbalanced; only Situation 2 has no acceleration.
2. Both situations are balanced ($F_{\text{net}}=0$); neither situation has acceleration. (correct answer)
3. Both situations are unbalanced; both must speed up.
4. Situation 1 is unbalanced because the book is not moving; Situation 2 is balanced because it is being pushed.

Question 14

1. $F_{\text{net}}=100\,\text{N}$; the rope accelerates toward the stronger side.
2. $F_{\text{net}}=0$; the rope has no acceleration (it stays at rest or keeps moving at constant velocity). (correct answer)
3. $F_{\text{net}}=50\,\text{N}$ left; the rope accelerates left.
4. $F_{\text{net}}=50\,\text{N}$ right; the rope accelerates right.

Question 15

1. $F_{\text{net}}=600\,\text{N}$ downward; the skydiver accelerates downward (speeds up). (correct answer)
2. $F_{\text{net}}=1000\,\text{N}$ upward; the skydiver accelerates upward.
3. $F_{\text{net}}=0$; the skydiver immediately moves downward at constant speed.
4. $F_{\text{net}}=600\,\text{N}$ upward; the skydiver slows down while falling.

Question 16

1. It speeds up to the right because a push always causes acceleration.
2. It slows down because friction is present, even though the forces are equal.
3. It continues moving to the right at constant velocity because $F_{\text{net}}=0$. (correct answer)
4. It must stop immediately because balanced forces mean zero velocity.

Question 17

1. Situation A is unbalanced because the ball is not moving; Situation B is balanced because the ball is moving.
2. Situation A is balanced with $F_{\text{net}}=0$ so it stays at rest; Situation B is unbalanced so it slows down (accelerates backward). (correct answer)
3. Situation A is balanced, so it must start rolling; Situation B is unbalanced, so it moves at constant speed.
4. Both situations are balanced because the weight and normal force cancel, so the ball's motion cannot change.

Question 18

1. $F_{\text{net}}=1400\,\text{N}$ downward, so acceleration is downward.
2. $F_{\text{net}}=0\,\text{N}$, so acceleration is $0$ and the speed stays constant. (correct answer)
3. $F_{\text{net}}=700\,\text{N}$ upward, so the parachutist slows down.
4. $F_{\text{net}}=0\,\text{N}$, so the parachutist must be at rest in the air.

Question 19

1. $F_{\text{net}}=20\,\text{N}$ to the left; the rope accelerates to the left. (correct answer)
2. $F_{\text{net}}=100\,\text{N}$ to the left; the rope moves left at constant speed.
3. $F_{\text{net}}=0\,\text{N}$; the rope accelerates because both teams are pulling.
4. $F_{\text{net}}=20\,\text{N}$ to the right; the rope accelerates to the right.

Question 20

1. Use two different carts and push each one with different strengths, without measuring the forces, and just describe what you think happened.
2. Use the same cart: first adjust the push so it matches friction and the cart moves at constant speed, then push harder than friction and measure how the cart's speed changes over time. (correct answer)
3. Use the same cart and only measure its mass, because mass alone determines whether forces are balanced.
4. Push the cart once and time how long it takes to stop; if it stops, that proves the forces were balanced the whole time.