Unit 6: Momentum Review 24-25

Unit 6: Momentum Review

RHS Physics

​For the following questions, identify if the statement is

(A) ALWAYS,

(S) SOMETIMES, or

(N) NEVER true.

What is Momentum?

It is affected by two factors.

​* Mass

​* Velocity

Multiple Choice

1. An object with mass will have momentum.

• Always

• Sometimes

• Never

​Sometimes: 1. An object with mass will have momentum.

• ​The object will only have momentum if the object is moving. If the object is moving, then it has a measurable velocity.

• ​Zero Velocity = Zero Momentum

Multiple Choice

2. The momentum of an object varies directly with the speed of the object

• Always

• Sometimes

• Never

Always: 2. The momentum of an object varies directly with the speed of the object

• Momentum and Velocity are directly proportional.

Multiple Choice

3. An object with less mass can have more momentum than an object with more mass.

• Always

• Sometimes

• Never

Sometimes: 3. An object with less mass can have more momentum than an object with more mass.

• Only if the object with less mass has a high enough velocity. Like Dash (little boy)

Multiple Choice

4. In a collision, the net impulse experienced by an object is equal to the change in its momentum.

• Always

• Sometimes

• Never

Always: 4. In a collision, the net impulse experienced by an object is equal to the change in its momentum.

Multiple Choice

 5. A force of 100 N acting for 0.1 seconds would provide the same impulse as a force of 5 N acting for 2.0 seconds.

• Always

• Sometimes

• Never

Always: 5. A force of 100 N acting for 0.1 seconds would provide the same impulse as a force of 5 N acting for 2.0 seconds.

Multiple Choice

 6. Two colliding objects will exert equal forces upon each other even if their mass is significantly different.

• Always

• Sometimes

• Never

Always: 6. Two colliding objects will exert equal forces upon each other even if their mass is significantly different.

• According to Newton's 3rd Law, when two objects interact with each other they impart equal and opposite forces.

Multiple Choice

7. Total momentum is always conserved between any two objects involved in a collision.

• Always

• Sometimes

• Never

Always: 7. Total momentum is always conserved between any two objects involved in a collision.

• According to the Law of Conservation of Momentum, the total momentum between 2 objects before a collision is the same total momentum between the 2 objects after a collision.

Multiple Choice

8. Momentum is conserved in an elastic collision but not in an inelastic collision.

• Always

• Sometimes

• Never

Never: 8. Momentum is conserved in an elastic collision but not in an inelastic collision.

• According to the Law of Conservation of Momentum, the total momentum between 2 objects before a collision is the same total momentum between the 2 objects after a collision.

• ​

• ​Momentum is always conserved between any 2 objects.

Multiple Choice

9. A car moving with a constant speed experiences no net force.

• Always

• Sometimes

• Never

Always: 9. A car moving with a constant speed experiences no net force.

• The forces on an object that is moving at constant velocity are balanced; therefore, no net force.

Multiple Choice

10. A truck driving along a highway road has a large quantity of momentum. If it moves at the same speed but has twice as much mass, its momentum is ___.

• halved

• quadrupled

• doubled

• unchanged

Doubled: 10. A truck driving along a highway road has a large quantity of momentum. If it moves at the same speed but has twice as much mass, its momentum is ___.

• ​momentum and mass are directly proportional

Multiple Choice

11. A 4 kg object has a momentum of 12 kg•m/s. The object's speed is ___ m/s.

• 3

• 4

• 12

• 48

3 m/s: 11. A 4 kg object has a momentum of 12 kg•m/s. The object's speed is 3 m/s.

• 12 = (4)(v)

• ​Divide both sides by 4

Multiple Choice

12. Which has more momentum, a 3 kg mass at 9 m/s or a 5 kg mass at 5 m/s?

• 3 kg mass

• 5 kg mass

3 kg mass: 12. Which has more momentum, a 3 kg mass at 9 m/s or a 5 kg mass at 5 m/s?

• p = (3)(9) = 27 kg•m/s

• ​The 3 kg mass has greater momentum.

• ​p = (5)(5) = 24 kg•m/s

Multiple Choice

13.An 8 kg mass moving at 8 m/s collides with a stationary 5 kg mass. After the collision, both the 8 and the 5 kg mass move off in the same direction. If the 8 kg mass is moving at 3 m/s after they collide, what is the speed of the 5 kg mass?

• $$V_{2f}$$ = 12 m/s

• $$V_{2f}$$ = 8 m/s

• $$V_{2f}$$ = 15 m/s

• $$V_{2f}$$ = 40 m/s

Multiple Choice

14. How much force is required to keep a 2-kg mass at a constant velocity?

• 9.8 Newtons

• 0 Newtons

• 2 Newtons

• 1

Zero Newtons: 14. How much force is required to keep a 2-kg mass at a constant velocity?

• Zero Newtons of Force

• ​

• ​Constant Velocity = balanced forces

Multiple Choice

15. A 50-kg boy on ice skates throws a 5-kg ball to the left. If the ball ends up going 20 m/s, how fast is the boy going as a result of throwing the ball?

• 10 m/s

• 2.75 m/s

• 2 m/s

2m/s: 15. A 50-kg boy on ice skates throws a 5-kg ball to the left. If the ball ends up going 20 m/s, how fast is the boy going as a result of throwing the ball?

​ Conservation of Momentum!

​Momentum of ball = Momentum of boy

Multiple Choice

16. Two cars that are 1500 kg each collide and stick together. The first car is moving 12.0 m/s to the right and the other is moving 16.0 m/s to the left. What is the velocity of the both cars after the collision?  Remember to include direction in your answer.

• -2 m/s, Left

• 2 m/s, Left

• -2 m/s, Right

• 2 m/s, Right

-2m/s, Left: 16. Two cars that are 1500 kg each collide and stick together. The first car is moving 12.0 m/s to the right and the other is moving 16.0 m/s to the left. What is the velocity of the both cars after the collision?  Remember to include direction in your answer.

The word "stick" is a hint that you should use the formula for inelastic collisions.

​Left = Negative Right = Positive

Multiple Choice

17.  If an 8 kg cart at rest is pushed by a 4N force to the right for an interval of 5 seconds, what will the cart’s velocity be at the end of the interval?

• -2.5 m/s, Left

• 2.5 m/s, Left

• -2.5 m/s, Right

• 2.5 m/s, Right

2.5 m/s, Right: 17.  If an 8 kg cart at rest is pushed by a 4N force to the right for an interval of 5 seconds, what will the cart’s velocity be at the end of the interval?