Impulse / MomentumProblem Set
A.Conceptual Questions
1)Explain two ways a heavy truck and a person on a skateboard can have the same momentum.
2)In stopping an object, how does the time of impact effect the magnitude of the force used to stop the object?
3)What is the relationship between an impulse on an object and the change in momentum of that object?
4)For a constant force, if the time the force is applied to an object doubles, the impulse will ______.
5)From question #4, by how much is the object’s momentum changed?
6)In a car crash, what is the advantage of an air bag in terms of impulse/change in momentum?
7)Why is the impulse greater on a falling object that bounces instead of an equally massive object that doesn’t bounce?
8)Explain why a tossed egg can be caught with a sagging sheet but not a piece of plywood?
9)A bug and the windshield of a moving car collide. Indicate which of the following statements are TRUE.
- The impact force on the bug and the car are the same magnitude.
- The impulse on the bug and the car are the same magnitude.
- The change in momentum of the bug and the car are the same magnitude.
- The change in velocity of the bug and the car are the same.
1) Not moving; truck really slow skateboard really fast. / 2) Small time; big force / 3) The impulse is equal to the change in momentum.
4) double / 5) double / 6) Change in momentum takes place over a longer time period.
7) The bouncing object has two changes in momentum instead of one for the one that doesn’t bounce. / 8) Change in momentum takes longer therefore a smaller force. / 9) a. True
b. True
c. True
d. False
B.Problems
1)(I) A compact car, mass = 725 kg, is moving at 100km/h.
a)What is the momentum of the car?
b)At what velocity must a larger car, mass = 2175 kg, be traveling in order to have the same momentum?
2)(I) A force of 6.0 N acts on a 3.0 kg object for 10.0 s.
a)What is the object's change in momentum?
b)What is the new velocity of the object if it started at rest?
3)(I) An 1100 kg car moves at 22.0 m/s. Neglecting friction, what breaking force is needed to stop the car in 20.0 s?
4)(I) A net force of 2000N acts on a rocket of mass 1000 kg. How long must the force be applied in order to increase the rocket's velocity from 10.0 m/s to 200.0 m/s?
5)(II) A snow scooter has a mass of 250 kg. A constant force acts upon the scooter for 1.0 minute. The scooter's velocity changes from 6.0 m/s to 28 m/s.
a)What change in momentum occurs?
b)What is the magnitude of the force acting on the scooter?
6)(II) A car weighing 15,680 N and moving at a speed of 20 m/s is slowed to a stop by a constant force of 640 N.
a)What is the initial momentum of the car?
b)How long must the breaking force be applied to the car?
7)(II) A constant force of 300 N acts on a 600 kg mass for 68 s. The initial velocity of the mass is 10.0 m/s. The direction of the force and the velocity is the same. What is the final velocity of the mass?
8)(II) A rocket of mass 2.0 x 104 kg starting from rest is accelerated by a net force of 1.5 x 105 N for 15.0 s. What is the final velocity of the rocket?
9)(II) A snowmobile has a mass of 250 kg. A constant force acts for 1.0 minute changing the velocity from 28.0 m/s to 6.0 m/s. What is the magnitude and direction of the force?
1)20100 kg m/s; 9.26 m/s / 2)60 kg m/s; 20. m/s / 3)–1210 N / 4)95 s / 5)a) 5500 kg m/s (b) 92 N6)32,000 kg m/s; 50. s / 7)44 m/s / 8)113 m/s / 9) 92 N,opposite motion
C.Conservation of Momentum:
10)(II) A 95 kg fullback, running at 8.2 m/s, collides in midair with a 128 kg defensive tackle moving in the opposite direction. Both players end up with zero speed.
(a)What as the fullback’s momentum before the collision?
(b)What as the change in the fullback’s momentum?
(c)What was the change in the tackle’s momentum?
(d)What was the tackle’s original momentum?
(e)How fast was the tackle moving originally?
11)(II) Marble A, mass 5.0 g, moves at a speed of 20.0 cm/s. It collides with a second marble, B, mass 10.0 g, moving at 10.0 cm/s in the same direction. After the collision, marble A continues with a speed of 8.0 cm/s in the same direction.
(a)Calculate the marbles’ momenta before the collision.
(b)Calculate the momentum of marble A after the collision.
(c)Calculate the momentum of marble B after the collision.
(d)What is the speed of marble B after the collision?
12)(II) A 0.105 kg puck moving at 48 m/s is caught by a stationary 75 kg goalie. With what speed does the goalie with the puck slide on the ice?
13)(II) A 35.0 g bullet strikes a 5.0 kg stationary wooden block and embeds itself in the block. The block and bullet fly off together at 8.6 m/s. What was the original velocity of the bullet?
14)(III) A 35.0 g bullet moving at 475 m/s strikes a 2.5 kg wooden block. The bullet passes through the block leaving at 275 m/s. If the block was originally at rest, with what velocity is the block moving after the bullet leaves?
15)(III) A 0.50 kg ball traveling at 6.0 m/s collides head on with a 1.00 kg ball moving in the opposite direction at 12.0 m/s. The 0.50 kg ball bounces back with a velocity of 14.0 m/s after the collision. What is the velocity (magnitude & direction) of the 1.00 kg ball after the collision?
16)(II) A green ball (m = 10.0 g) moving with a velocity of 20.0 cm/s catches up to and collides with a red ball (m = 20.0 g) moving along the same line with a velocity of 10.0 cm/s. After the collision, the green ball is still moving in its original direction with a velocity of only 8.0 cm/s. Determine the final velocity of the red ball.
17)(II) A 700 kg car traveling at 20.0 m/s collides with a stationary 1400 kg truck. The two vehicles interlock and travel together. What is the final velocity of the car?
18)(II) A 40.0 kg projectile leaves a 2000 kg launcher with a velocity of 800 m/s. What is the recoil velocity of the launcher?
19)(II) Upon launching, a model rocket expels 50.0 g of fuel from its exhaust at an average velocity of 600 m/s. If the rocket moves upward at 7.5 m/s, what is the mass of the rocket?
20)(II) Two campers dock a canoe. One camper(80.0 kg) steps onto the dock moving at 4.0 m/s. The canoe and other camper move backwards at 2.9 m/s. If the second camper’s mass is 75.0 kg, what is the mass of the canoe?
21)(II) Two students (90.0 kg and 60.0 kg) on roller skates face-to-face push against each other. The 90.0 kg student moves at 5.0 m/s just after their hands lose contact.
(a)What is the velocity of the other student?
(b)What average force was exerted on each student if they were in contact for 0.003 s?
10)(a) 779 kg m/s (b) – 779 kg m/s (c)+ 779 kg m/s (d) -779 kg m/s (e) -6.1 m/s11)(a) 100 g cm/s (b) 40 g cm/s (c) 160 g cm/s (d) 16 cm/s
12)0.067 m/s / 13)1200 m/s / 14)2.8 m/s / 15)2.0 m/s opposite direction
16)16 cm/s / 17)6.7 m/s / 18)16 m/s backwards / 19)4.0 kg
20)35 kg / (a) 7.5 m/s backwards (b) 1.5 x 105 N
D.Elastic & Inelastic Collisions:
22)In an inelastic collision, ______is/are conserved.
23)In an elastic collision, ______is/are conserved.
24)(II) A 0.015 kg marble moving to the right at 22.5 cm/s collides with a 0.015 kg marble moving to the left at 18.0 cm/s. After the collision, the first marble moves to the left at 18.0 cm/s.
(a)What is the final velocity of the second marble after the collision?
(b)Is the collision elastic or inelastic?
23) (III) A 0.25 kg arrow with a velocity of 12 m/s to the west strikes and pierces the center of a 6.8 kg target.
a)What is the final velocity of the combined mass?
b)What is the decrease in kinetic energy?
22) momentum / 23) momentum and kinetic energy24) (a) 22.5 cm/s to the right (b) elastic / 25) (a) 0.43 m/s (b) 17.35 J