6.2 Conservation of Momentum

If a reckless ice skater collides with another skater who is standing on the ice, is it possible for both skaters to be at rest after the collision?

• Yes, it is possible if they stick together and their combined momentum is zero.

• No, it is not possible due to the conservation of momentum.

• Yes, if external forces act on them to bring them to rest.

• No, because ice is frictionless and they will keep moving.

Tags

NGSS.HS-PS2-2

A spacecraft undergoes a change of velocity when its rockets are fired. How does the spacecraft change velocity in empty space, where there is nothing for the gases emitted by the rockets to push against?

• The gases push against the spacecraft itself, changing its velocity.

• The gases push against the vacuum of space, changing its velocity.

• The gases do not need to push against anything to change the spacecraft's velocity.

• The gases push against the gravitational field, changing its velocity.

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NGSS.HS-PS2-1

A 76 kg boater, initially at rest in a stationary 45 kg boat, steps out of the boat and onto the dock. If the boater moves out of the boat with a velocity of 2.5 m/s to the right, what is the final velocity of the boat?

• -4.22 m/s

• -3.33 m/s

• -2.5 m/s

• -1.67 m/s

Tags

NGSS.HS-PS2-2

A 63.0 kg astronaut is on a spacewalk when the tether line to the shuttle breaks. The astronaut is able to throw a spare 10.0 kg oxygen tank in a direction away from the shuttle with a speed of 12.0 m/s, propelling the astronaut back to the shuttle. Assuming that the astronaut starts from rest with respect to the shuttle, find the astronaut’s final speed with respect to the shuttle after the tank is thrown.

• 1.9 m/s

• 2.0 m/s

• 2.1 m/s

• 2.2 m/s

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NGSS.HS-PS2-1

NGSS.HS-PS2-2

An 85.0 kg fisherman jumps from a dock into a 135.0 kg rowboat at rest on the west side of the dock. If the velocity of the fisherman is 4.30 m/s to the west as he leaves the dock, what is the final velocity of the fisherman and the boat?

• 1.72 m/s to the west

• 2.15 m/s to the west

• 3.45 m/s to the west

• 4.30 m/s to the west

Tags

NGSS.HS-PS2-2

Each croquet ball in a set has a mass of 0.50 kg. The green ball, traveling at 12.0 m/s, strikes the blue ball, which is at rest. Assuming that the balls slide on a frictionless surface and all collisions are head-on, find the final speed of the blue ball in each of the following situations: a. The green ball stops moving after it strikes the blue ball. b. The green ball continues moving after the collision at 2.4 m/s in the same direction.

• a. 12.0 m/s, b. 2.4 m/s

• a. 6.0 m/s, b. 9.6 m/s

• a. 6.0 m/s, b. 4.8 m/s

• a. 12.0 m/s, b. 4.8 m/s

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NGSS.HS-PS2-2

A boy on a 2.0 kg skateboard initially at rest tosses an 8.0 kg jug of water in the forward direction. If the jug has a speed of 3.0 m/s relative to the ground and the boy and skateboard move in the opposite direction at 0.60 m/s, find the boy’s mass.

• 4.0 kg

• 6.0 kg

• 8.0 kg

• 10.0 kg

Tags

NGSS.HS-PS2-2

A 44 kg student on in-line skates is playing with a 22 kg exercise ball. Disregarding friction, what happens when the student throws the ball horizontally, causing the student to glide back at 3.5 m/s?

• The student moves forward at 3.5 m/s.

• The student remains stationary.

• The student glides back at 3.5 m/s.

• The student glides back at a different speed.

Tags

NGSS.HS-PS2-1

NGSS.HS-PS2-2

What happens to the ball in part (a) in terms of the momentum of the student and the momentum of the ball?

• The momentum of the ball increases while the student's momentum decreases.

• The momentum of the ball decreases while the student's momentum increases.

• Both the ball and the student maintain their momentum.

• The momentum of the ball and the student are exchanged.

Tags

NGSS.HS-PS2-2

The student is initially at rest. The student then catches the ball, which is initially moving to the right at 4.6 m/s. What is the velocity of the student after catching the ball?

• 0 m/s

• 2.3 m/s to the right

• 4.6 m/s to the right

• 9.2 m/s to the right

Tags

NGSS.HS-PS2-2