Question 1

A tiger is running in a straight line.If we double both the mass and speed of the tiger,the magnitude of its momentum will increase by what factor?

Accepted Answer

The momentum of an object is given by the product of its mass and velocity. Mathematically, we can write:

p = mv

where p is momentum, m is mass, and v is velocity.

If we double both the mass (m) and speed (v), the new momentum (p') can be calculated as follows:

p' = (2m) x (2v)
   = 4mv

So, the magnitude of the momentum will increase by a factor of 4. Therefore, the correct answer is C) 4.

Question 2

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

Accepted Answer

Momentum is defined as mass times velocity, which has units of kg∙m/s. Additionally, impulse (N∙s) is equivalent to a change in momentum.

Question 3

A rubber ball and a lump of clay have equal mass.They are thrown with equal speed against a wall.The ball bounces back with nearly the same speed with which it hit.The clay sticks to the wall.Which one of these objects experiences the greater momentum change?

Accepted Answer

The momentum change of an object is equal to the force applied on it multiplied by the time of application. When the ball hits the wall, it experiences a strong force for a very short period of time, causing a significant momentum change. When it bounces back, it experiences an equal but opposite force, causing the momentum change to be nearly the same in magnitude. However, when the clay hits the wall it experiences a strong force for a short period of time, causing a significant momentum change, but it does not bounce back, meaning its momentum change is not reversed. Therefore, the momentum change of the ball is greater than that of the clay.

Question 4

A small car meshes with a large truck in a head-on collision.Which of the following statements concerning the magnitude of the average force during the collision is correct?

Accepted Answer

According to Newton's third law of motion, for every action, there is an equal and opposite reaction. This means that the magnitude of the force exerted by the small car on the truck is equal to the magnitude of the force exerted by the truck on the small car during the collision.

Question 5

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

Accepted Answer

In a collision, the momentum of the car and the truck individually is not conserved as they experience external forces due to the collision. However, the total momentum of the car-truck system is conserved, as there are no external forces acting on the system. The speeds of the car and the truck may not change by the same amount during the collision, so statement C is not necessarily true. Statements A, B, and D are incorrect as they suggest that the momentum of each object is conserved individually, which is not true in a collision with external forces.

Question 6

Identical forces act for the same length of time on two different objects.The magnitude of the change in momentum of the lighter object is

Accepted Answer

According to the law of conservation of momentum, the total momentum of the system before and after the interaction should be the same. As the forces acting on both objects are identical for the same length of time, the change in momentum of both objects should be the same. Therefore, the magnitude of the change in momentum of the lighter object is exactly equal to the magnitude of the change in momentum of the larger mass.

Question 7

A very elastic rubber ball is dropped from a certain height and hits the floor with a downward speed v.Since it is so elastic,the ball bounces back with the same speed v going upward.Which of the following statements about the bounce are correct? (There could be more than one correct choice. )

Accepted Answer

CThe magnitude of the ball's momentum is the same just before and just after the bounce because momentum is mass times velocity, and only the direction of the velocity changes, not its magnitude. Momentum is conserved during the bounce because the change in momentum (which involves the ball going from downward to upward motion) is equal and opposite, assuming no external forces act on the system other than the normal force from the floor, which is an internal force for the system consisting of the ball and the Earth.

Question 8

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

Accepted Answer

Impulse is the change in momentum and is measured in units of momentum (kg∙m/s) or force applied over time (N∙s).

Question 9

In an inelastic collision involving an isolated system,the final total momentum is

Accepted Answer

In an isolated system, there is no external force acting on the bodies, hence the momentum remains conserved. Even during an inelastic collision, where the bodies stick together and move as a single object, the total momentum before and after the collision remains the same. Hence the correct answer is A) exactly the same as the initial momentum.

Question 10

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

The long barrel in the Big Bertha cannon was used to allow the force of the expanding gases from the gunpowder to act for a longer time. This increased the velocity and range of the shells fired by the cannon.

Question 11

You are standing on a skateboard,initially at rest.A friend throws a very heavy ball towards you.You have two choices about what to do with the ball: either catch the ball or deflect it back toward your friend with the same speed as it was originally thrown.Which choice should you make in order to maximize your speed on the skateboard?

Accepted Answer

According to the law of conservation of momentum, the total momentum of a system of objects remains constant if no external forces act on it. Initially, the momentum of the system (you and the skateboard) is zero. When your friend throws the heavy ball towards you, the momentum of the system changes. If you catch the ball, you increase the momentum of the system in the direction of the ball's motion, causing you and the skateboard to move backward. On the other hand, if you deflect the ball back with the same speed, you increase the momentum of the system in the backward direction, causing you and the skateboard to move forward with greater speed. Therefore, deflecting the ball back towards your friend with the same speed as it was thrown is the better choice to maximize your speed on the skateboard.

Question 12

A very light ping-pong ball moving east at a speed of 4 m/s collides with a very heavy stationary bowling ball.The Ping-Pong ball bounces back to the west,and the bowling ball moves very slowly to the east.Which object experiences the greater magnitude impulse during the collision?

Accepted Answer

According to Newton's third law of motion, for every action, there is an equal and opposite reaction. This means that the magnitude of the impulse experienced by the ping-pong ball and the bowling ball during their collision is the same, even though their masses and the changes in their velocities differ.

Question 13

The momentum of an isolated system is conserved

Accepted Answer

The law of conservation of momentum states that the momentum of an isolated system remains constant, whether the collision is elastic or inelastic. In elastic collisions, the kinetic energy is also conserved, whereas in inelastic collisions, some of the kinetic energy is converted into other forms of energy, such as heat or sound. Therefore, the momentum of an isolated system is conserved in both elastic and inelastic collisions.

Question 14

A 5-kg ball collides inelastically head-on with a 10-kg ball,which is initially stationary.Which of the following statements is true? (There could be more than one correct choice. )

Accepted Answer

The 5-kg ball experiences a greater change in velocity due to its smaller mass. However, the change in momentum for both balls is equal in magnitude because momentum is conserved in collisions.

Question 15

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

According to the law of conservation of momentum, the magnitude of momentum change is the same for both the truck and the small car during the collision. This is because the total momentum of the system (truck + car) before the collision must equal the total momentum of the system after the collision, assuming no external forces are acting on the system.

Question 16

Three cars,car X,car Y,and car Z,begin accelerating from rest at the same time.Car X is more massive than car Y,which is more massive than car Z.The net accelerating force exerted on each car is identical.After 10 seconds,which car has the most amount of momentum?

Accepted Answer

Momentum is the product of mass and velocity. Since all three cars start from rest and are subjected to the same net accelerating force, they will all gain the same amount of momentum over the 10 seconds, regardless of their mass differences. This is because the acceleration (a result of the net force, as per Newton's second law, F=ma) will be inversely proportional to their masses, leading to a situation where the lighter cars accelerate more but have less mass, and the heavier cars accelerate less but have more mass, resulting in the same momentum for all.

Question 17

Consider two less-than-desirable options.In the first you are driving 30 mph and crash head-on into an identical car also going 30 mph.In the second option you are driving 30 mph and crash head-on into a stationary brick wall.In neither case does your car bounce back from the thing it hits,and the collision time is the same in both cases.Which of these two situations would result in the greater impact force on your car?

Accepted Answer

The impact force on your car would be the same in both cases because the change in velocity and collision time are the same, according to Newton's third law of motion.

Question 18

Two friends are standing on opposite ends of a canoe that is initially at rest with respect to a frictionless lake.The person in the front throws a very massive ball toward the back,and the person in the back catches it.After the ball is caught,the canoe is

Accepted Answer

The system's center of mass remains unchanged because there are no external forces. The internal action of throwing and catching the ball doesn't affect the overall motion of the canoe.

Question 19

A rocket explodes into two fragments,one 25 times heavier than the other.The magnitude of the momentum change of the lighter fragment is

Accepted Answer

The law of conservation of momentum states that the total momentum of a closed system is constant if no external forces act on it. When the rocket explodes, the momentum of the system (rocket) before the explosion is equal to the total momentum of the fragments after the explosion. Since momentum is a vector quantity, the momentum change of the lighter fragment must be equal in magnitude and opposite in direction to the momentum change of the heavier fragment to conserve the total momentum of the system.

Question 20

In a collision between two unequal masses,which mass receives a greater magnitude impulse?

Accepted Answer

In a collision, both masses receive equal magnitudes of impulse due to Newton's third law, which states that for every action, there is an equal and opposite reaction. This means the force exerted on each object for the same amount of time is equal, resulting in equal impulses.

Quiz 9: Linear Momentum and Collisions