Momentum and Impulse

Momentum and Impulse

MOMENTUM

- product of mass and velocity of an object

- vector quantity - has a magnitude and direction

* has the same direction as the velocity

MOMENTUM

p = mv

where:

p = momentum in kg.m/s

m = mass in kg

v = velocity in m/s

MOMENTUM

* All objects have mass. So, if an object is moving then it has momentum.

* Mass is in motion.

* Momentum is inertia in motion.

"I couldn't stop my MOMENTUM."

• Momentum involves MOTION.

• Momentum involves MASS.

Multiple Choice

When the speed of an object is doubled, what happens to its momentum?

• remains unchanged in accordance with the conservation of momentum

• doubles

• quadruples

• decreases

Multiple Choice

Which takes more force to catch, a bowling ball or a ping pong ball?

• bowling ball because it has more momentum

• ping pong ball because it has more momentum

• both require the same amount of force when catching

• bowling ball because it has less momentum

Multiple Choice

A 50 kg ball rolls down the street at 5 m/s. Calculate the momentum of the ball.

• 55 kg.m/s

• 100 kg.m/s

• 250 kg.m/s

• 500 kg.m/s

Multiple Choice

A biker with a mass of 75 kg moves along the path with a constant velocity of 5 m/s. What is the biker's momentum?

• 25 m/s

• 375 m/s

• 25 kg.m/s

• 375 kg.m/s

Multiple Choice

A runner has a momentum of 670 kg.m/s and is traveling at a velocity of 9 m/s. What is his mass?

• 6 030 kg

• 0.013 4 kg

• 74.4 kg

• 80 kg

Multiple Choice

An object with a mass of 2 000 kg at rest has what momentum?

• 2 000 kg m/s

• 0 kg m/s

• 2 000 kg

• 2 000 m/s

Multiple Choice

A 50 kg ball rolls down the street at 5 m/s. Calculate the momentum of the ball.

• 55 kg.m/s

• 100 kg.m/s

• 250 kg.m/s

• 500 kg.m/s

Multiple Choice

A 10 kg toy truck moves at 5 m/s, East. It collides head-on with a 5 kg toy car moving 10 m/s moving west. What is the total momentum of the system?

• 0 kg.m/s

• 30 kg.m/s

• 50 kg.m/s

• 10 kg.m/s

How hard is it to stop a moving object?

Do you have any idea?

The momentum of an object will change if either the mass or the velocity or both the mass and the velocity change. If the momentum changes while the mass remains unchanged, as in most often the case, then the velocity changes. ACCELERATION occurs. What produces acceleration?

FORCE

To change the momentum of an object, both FORCE and TIME during which the force acts are important.

This is called IMPULSE.

Multiple Select

What is the unit for impulse?

• kg

• $$N\cdot s$$

• N

• m/s

• $$kg\cdot\frac{m}{s}$$

Multiple Choice

What is the purpose of crumple zones in cars?

• decrease time of impact

• increase force of impact

• increase the time of impact

• decrease the impulse during impact

Multiple Choice

What do softer landings tend to increase?

• impact force

• force

• collision time

• change in momentum

Multiple Choice

Cart A is pulled with a 2 N force for 2 s, and Cart B is pulled with a 1 N force for 3 s. Which cart experiences the GREATER impulse?

• Cart B

• Cart A

• they are the same

Multiple Choice

What does the impulse-momentum theorem state?

• The impulse on an object is equal to the change in momentum it causes.

• The force on a moving object is equal to the magnitude of the impulse.

• The impulse on an object is greater than the change in momentum it causes.

• The impulse on an object is less than the change in momentum it causes.

Multiple Choice

A 5 N force is applied to a 3 kg ball to change its velocity from +9 m/s to +3 m/s. What is the impulse on the ball?

• - 2.5 N.s

• - 10 N.s

• - 18 N.s

• - 45 N.s

Multiple Choice

The velocity of a 975-kg car is changed from 12.0 m/s to 27.0 m/s in 15 s by an external, constant force. What is the magnitude of the force?

• 9.75 x 10² N

• 1.46 x10⁴ N

• 9.75 x10³ N

• 975 kg·m/s

Multiple Choice

A constant force of 4.5 N acts on a 7.2-kg object for 10.0 s. What is the change in the object's velocity?

• 6.3 m/s

• 3.2 m/s

• 1.2 m/s

• 4.33 m/s

Multiple Choice

A boy kicks a football with a force of 20 N, the time the force acts is 0.3 s. Calculate the impulse on the ball.

• 1 N.s

• 6 N.s

• 66 N.s

• cannot be determined

Multiple Choice

A 40-kg mass is moving across a horizontal surface at 5.0 m/s. What is the magnitude of the net force required to bring the mass to a stop in 8.0 s?

• 1 N

• 40 N

• 25 N

• 5 N

Multiple Choice

The velocity of a 975-kg car is changed from 12.0 m/s to 27.0 m/s in 15 s by an external, constant force. What is the magnitude of the force?

• 9.75 x 10² N

• 1.46 x 10⁴ N

• 9.75 x 10³ N

• 975 kg.m/s

Multiple Choice

If an air bag changes a 60 kg person's speed from 40.0 m/s to 0.0 m/s, what impulse must act on the person?

• 2 400 kg.m/s

• 1.5 kg.m/s

• 0.67 kg.m/s

• 1 500 kg.m/s

Multiple Choice

A boy kicks a football with a force of 20 N, the time the force acts for is 0.3 s. Calculate the impulse on the ball.

• 1 N.s

• 6 N.s

• 66 N.s

• 0.001 5 N.s