Question 1

On a horizontal frictionless air table,a puck runs into an ideal horizontal spring that is fastened to the table.The puck compresses the spring by 15 cm before coming to rest.During the compression process,which quantities are conserved?

Accepted Answer

A) only the momentum of the puck 
B) only the kinetic energy of the puck 
C) only the mechanical energy (kinetic plus potential)of the puck 
D) the momentum and the mechanical energy of the puck 
E) the momentum and the kinetic energy of the puck

Question 2

Which of the following quantities are units of impulse? (There could be more than one correct choice. )

Accepted Answer

A) N ∙ m 
B) kg ∙ s/m 
C) kg ∙ m/s 
D) N ∙ s 
E) kg ∙ m2/s2

Question 3

If you want to double the kinetic energy of a gas molecule,by what factor must you increase its momentum?

Accepted Answer

A)   
B) 2 
C) 2  
D) 4 
E) 16

Question 4

A block of mass m = 4.4 kg,moving on frictionless surface with a speed vi = 9.2m/s,  Makes a sudden perfectly elastic collision with a second block of mass Mass shown in the figure.The second block is originally at rest.Just after the collision,the 4.4-kg block recoils with a speed of vf=2.5m/s. What is the mass M of the second block?

Accepted Answer

A) 7.7 kg 
B) 0 kg 
C) 0...kg 
D) 0.. kg 
E) 0.kg

Question 5

A small car meshes with a large truck in a head-on collision.Which of the following statements concerning the magnitude of the momentum change during the collision is correct? (There could be more than one correct choice. )

Accepted Answer

A) The truck experiences the greater magnitude momentum change. 
B) The small car experiences the greater magnitude momentum change. 
C) The small car and the truck experience the same magnitude momentum change. 
D) The magnitude of the momentum change experienced by each one is inversely proportional to its mass. 
E) The magnitude of the momentum change experienced by each one is directly proportional to its mass.

Question 6

A firecracker explodes in midair and breaks up into many fragments.Which of the following statements are true regarding conditions immediately before and immediately after the explosion?
I.The total momentum of the fragments is equal to the original momentum of the firecracker.
II.The total kinetic energy of the fragments is equal to the original kinetic energy of the firecracker.

Accepted Answer

A) Statement I only 
B) Statement II only 
C) Both Statement I and Statement II 
D) Neither statement is true.

Question 7

An 8.0-g bullet is suddenly shot into a 4.0-kg block,at rest on a frictionless horizontal surface,as shown in the figure.The bullet remains lodged in the block.The block then moves against a spring and compresses it by 8.9 cm.The force constant (spring constant)of the spring is 
What is the magnitude of the impulse on the block (including the bullet inside)due to the spring during the entire time interval during which the block compresses the spring?

Accepted Answer

A) 13 N ∙ s 
B) 12 N ∙ s 
C) 10 N ∙ s 
D) 8.3 N ∙ s 
E) 6.7 N ∙ s

Question 8

A 2.0-kg mass moving at 5.0 m/s suddenly collides head-on with a 3.0-kg mass at rest.If the collision is perfectly inelastic,what is the speed of the masses just after the collision?

Accepted Answer

A) 10 m/s 
B) 2.5 m/s 
C) 2.0 m/s 
D) 0 m/s,since the collision is inelastic

Question 9

Astronaut Jennifer's lifeline to her spaceship comes loose and she finds herself stranded,"floating" 100 m from the mothership.She suddenly throws her 2.00-kg wrench at 20 m/s in a direction away from the ship.If she and her spacesuit have a combined mass of 200 kg,how long does it take her to coast back to her spaceship?

Accepted Answer

A) 1000 s 
B) 750 s 
C) 500 s 
D) 250 s 
E) 2.50 min

Question 10

A forklift pushes a 100-kg crate,starting from rest,with a horizontal force of magnitude F.The graph in the figure shows the x component of this force as a function of time.What is the instantaneous velocity of the crate at time t = 10 s?

Accepted Answer

A) 25 cm/s 
B) 0.00 cm/s 
C) 75 cm/s 
D) -25 cm/s 
E) -75 cm/s

Question 11

A block of mass m = 9.0 kg and speed V and is behind a block of mass M = 27 kg and speed of 
As shown int the figure.The surface is frictionless,and the blocks suddenly collide and couple.After the collision,the blocks have a common speed of 0.90 m/s.How much kinetic energy of the blocks is lost due to the collision?

Accepted Answer

A) 8.6 J 
B) 2.0 J 
C) 4.6 J 
D) 11 J 
E) 31 J

Question 12

Two ice skaters suddenly push off against one another starting from a stationary position.The 45-kg skater acquires a speed of 0.375 m/s relative to the ice.What speed does the 60-kg skater acquire relative to the ice?

Accepted Answer

A) 0.50 m/s 
B) 0.28 m/s 
C) 0.38 m/s 
D) 0.75 m/s 
E) 0.00 m/s

Question 13

Two astronauts,of masses 60 kg and 80 kg,are initially right next to each other and at rest in outer space.They suddenly push each other apart.What is their separation after the heavier astronaut has moved 12m?

Accepted Answer

A) 9.0 m 
B) 16 m 
C) 21 m 
D) 24 m 
E) 28 m

Question 14

During World War I,Germany used a "Big Bertha" cannon to hurl shells into Paris 30 miles away.This gun also had a very long barrel.What was the reason for using a long barrel in these guns?

Accepted Answer

A) to exert a larger force on the shells 
B) to reduce frictional losses 
C) to allow the force of the expanding gases from the gunpowder to act for a longer time 
D) to increase the force exerted on the bullet due to the expanding gases from the gunpowder 
E) to reduce the force exerted on the bullet due to the expanding gases from the gunpowder

Exam 9: Linear Momentum and Collisions