Momentum, Impulse and Conservation of Momentum

What happens to the momentum of an object if its mass becomes lighter?

• Momentum increases.

• Momentum decreases.

• Momentum is unchanged.

• Momentum is not affected.

Answer explanation

Momentum is directly proportional to the object's mass and also its velocity. Thus the greater an object's mass or the greater its velocity, the greater its momentum.

When comparing the momentum of two objects, which of the following statements is correct?

• The less massive object will have less momentum if the velocities are the same.

• The object with the higher velocity will have less momentum if the masses are equal.

• The object with the higher velocity will have less momentum if the masses are equal.

• The more massive object will have less momentum if the velocities are equal.

• the time interval divided by the net external force

• the product of the force applied to the object and the time interval

• the product of the mass of the object and the time interval

• the net external force divided by the time interval.

How do seatbelts and airbags in vehicles help to lessen the damage or risks during collision?

• They limit the stopping time

• They amplify the impact force

• They reduce the impact force.

• They exert a greater stopping force

Answer explanation

The air bag reduces the impulse by reducing the change in the passengers momentum. The air bag reduces the force by increasing the time it takes the passenger to stop moving.

Which two characteristics do closed systems possessed?

I. No net external force acts on it

II. The momentum of each object in the system remains constant

III. The system does not gain or lose momentum

IV. Objects can enter, but not leave the system

• i and ii

• i and iii

• i and iv

• ii and iii

The impulse experienced by a body is equivalent to the body’s change in ______________.

• force

• kinetic energy

• momentum

• velocity

Which of the following collisions doesn’t show elastic collision?

• collision of billiard balls.

• collision of gas particles inside a close container

• collision of a ball and the ground when a player is bouncing it.

• collision of two cars that stick together after the collision.

What is the impulse equivalent to?

• change in momentum

• force multiplied by time

• Both a and b

• Neither a nor b

What causes momentum change in objects or bodies?

• change in gravity and friction

• change in force and mass

• change in acceleration and weight

• change in mass and velocity

Answer explanation

Changes in momentum happen every time. It occurs when there is a change of the objects’ mass and velocity, or both

If there is no external force acting on the system, what happens to the momentum of moving vehicles before and after collision?

• speeds up

• slows down

• remains unchanged

• transforms into energy

Answer explanation

In an isolated system, the total momentum does not change if no net external forces (like friction) act on it.