Physics: Momentum and Collisions

Question 1

What is the equation for momentum?

Answer 1

P=m x v

Question 2

What does p stand for?

Answer 2

Momentum

Question 3

What is momentum?

Answer 3

A quantity defined as the product of the mass and velocity of an object.

Question 4

A deer with a mass of 146 kg is running head-on towards you with a speed of 17 m/s. You are going north. Find the momentum of the deer

Answer 4

2482 kg*m/s South

Question 5

A 21 kg child on a 5.9 kg bike is riding with a velocity of 4.5 m/s to the Northwest. What is the momentum of the bike, the child, and both of them?(Remember sig figs)

Answer 5

Child: 95 kgm/s northwest
Bike: 27 kgm/s northwest
Both: 120 kg*m/s northwest

Question 6

What velocity must a 1210 kg car have in order to have the same velocity of a pickup truck that has a mass of 2250 and a velocity of 25 m/s east?

Answer 6

46 m/s east

Question 7

What is the impulse-momentum theorem?

Answer 7

F x delta t = delta p or force times change in time equals change in momentum

Question 8

What is the impulse in the impulse momentum theorem?

Answer 8

F x delta t

Question 9

How was Newton’s second law originally expressed?

Answer 9

Force = change in momentum/change in time

Question 10

A 0.50 kg football is thrown with a velocity of 15 m/s to the right. A stationary receiver catches the ball and brings it to rest in 0.020 s. What is the force exerted on the ball by the receiver?

Answer 10

380 N to the left

Question 11

An 82 kg man drops from rest on a diving board 3.0 m above the surface of the water and comes to rest 0.55 s after reaching the water. What is the net force on the diver as he is brought to rest? (Assume g = 9.81 m/s^2)

Answer 11

0.78 N up

Question 12

A 0.40 kg soccer ball approaches a player horizontally with a velocity of 18 m/s north. The player strikes the ball and causes it to move in the opposite direction at a velocity of 22 m/s. What impulse was delivered to the ball by the player?

Answer 12

16 kg*m/s south

Question 13

A 0.50 kg object is at rest. A 3.00 N force to the right acts on the object during a time interval of 1.50 s.

a. What is the velocity of the object at the end of this interval?
b. At the end of this interval, a constant force of 4.00 N to the left is applied for 3.00 s. What is the velocity at the end of the 3.00 s?

Answer 13

a. 9 m/s

b. -15 m/s

Question 14

The speed of a particle is doubled.

  a. By what factor is its momentum changed?
  b. What happens to its kinetic energy?

Answer 14

a. It is doubled

b. quadrupled

Question 15

A pitcher claims he can throw a 0.145 baseball with as much momentum as a speeding bullet. Assume that a 3.00 g bullet moves at a speed of 1.5x10^3 m/s

a. What must the baseball's speed be if the pitcher's claim is valid?
b. Which has the greater kinetic energy, the ball or the bullet?

Answer 15

a. 31.034 m/s

b. The ball

Question 16

A 0.42 soccer ball is moving downfield with a velocity of 12 m/s. A player kicks the ball so that it has a final velocity of 18 m/s downfield.

a. What is the change in the ball's momentum?
b. Find the constant force exerted by the player's foot if the two are in contact for 0.020 s.

Answer 16

a. 2.52 kg*m/s downfield

b. 126 N

Question 17

What is the unit for momentum?

Answer 17

kg*m/s

Question 18

When a force is exerted on an object, does a large force always produce a larger change in the objects momentum than a smaller force? Explain.

Answer 18

No, because if the smaller force is applied over a longer amount of time, it can have a larger effect, due to the impulse momentum theory.

Question 19

What is the law of conservation of momentum?

Answer 19

m1v1,i +m2v2,i = m1v1,f + m2v2,f

Total initial momentum = total final momentum

Question 20

A 63.0 kg astronaut is on a space walk when his 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 respective to the shuttle, find the astronaut’s final speed with respect to the shuttle after the tank is thrown.

Answer 20

1.9 m/s

Question 21

An 85 kg fisherman jumps from a dock into a 135 kg rowboat at rest an 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?

Answer 21

1.66 m/s to the west

Question 22

What is a perfectly inelastic collision?

Answer 22

a collision in which two objects stick together after colliding

Question 23

Is kinetic energy conserved in perfectly inelastic collisions?

Answer 23

No

Question 24

What is the equation for perfectly inelastic collisions?

Answer 24

m1v1,i+m2v2,i=(m1+m2)vf

Question 25

A 1500 kg car travelling at 15.0 m/s to the south collides with a 4500 kg truck initially at rest at a stoplight. the car and truck stick together and move together after the collision. What is the final velocity of the two-vehicle mass?

Answer 25

3.8 m/s south

Question 26

What is an elastic collision?

Answer 26

A collision in which the total momentum and total kinetic energy are conserved.

Question 27

Is kinetic energy conserved in elastic collisions?

Answer 27

Yes