Momentum and Impulse Review

Front

If the momentum of an object changes and its mass remains constant, what can be inferred?

Back

All of the above: its velocity is changing, there is a force acting on it, it is accelerating.

Answer explanation

If momentum changes with constant mass, it indicates a change in velocity, meaning the object is accelerating. This also implies a force is acting on it, making 'all of the above' the correct choice.

Front

The momentum change of an object is equal to the

Back

impulse acting on it

Answer explanation

The momentum change of an object is defined by the impulse acting on it, which is the product of the force applied and the time duration of that force. Thus, the correct answer is the impulse acting on it.

Front

A car traveling along the road needs a force to stop, more force is required when the car has ______________

Back

all of these

Answer explanation

A car requires more force to stop when it has more momentum (mass times velocity), more mass, or less stopping distance. Therefore, all these factors contribute to the need for increased stopping force.

Front

Which of the following has the largest momentum: a large truck parked in a parking lot, a pickup truck traveling down the highway, the science building at your school, a dog running down the street?

Back

a pickup truck traveling down the highway

Answer explanation

Momentum is the product of mass and velocity. The pickup truck traveling down the highway has both significant mass and velocity, making its momentum larger than the other options, which are either stationary or moving slower.

Front

A ball player moves his hand backward to catch a ball. This reduces the force on the hand by:

Back

increasing the time of impact

Answer explanation

A ball player moves his hand backward to increase the time of impact with the ball. This longer duration reduces the force experienced by the hand, as force is the change in momentum over time.

Front

The reason padded dashboards are used in cars is that they...

Back

increase the time of impact

Answer explanation

Padded dashboards are designed to increase the time of impact during a collision. By extending the duration over which the force is applied, they help reduce the severity of injuries to passengers.

Front

What does the law of conservation of momentum state?

Back

The total momentum in an isolated system is conserved.

Answer explanation

The law of conservation of momentum states that in an isolated system, the total momentum remains constant over time, meaning it is conserved. This is the correct choice among the options provided.

Front

A car runs into a resting identical car and they stick together. How is the final velocity (Vf) different from the initial velocity (Vi)?

Back

half as large

Answer explanation

When two identical cars collide and stick together, momentum is conserved. The final velocity (Vf) of the combined mass is half the initial velocity (Vi) of the moving car, making Vf half as large as Vi.

Front

A 5kg ball has a momentum of 30kgm/s. What is the ball's speed?

Back

6 m/s

Answer explanation

Momentum is calculated as mass times velocity (p = mv). Given momentum (30 kgm/s) and mass (5 kg), we can find speed: v = p/m = 30 kgm/s / 5 kg = 6 m/s. Thus, the correct answer is 6 m/s.

Front

Why is the speed of a cannon's recoil small after launching a cannonball?

Back

The mass of the cannon is larger.

Answer explanation

The cannon's recoil speed is small because it has a larger mass compared to the cannonball. According to the law of conservation of momentum, a larger mass results in a smaller velocity when momentum is conserved.