Momentum Introduction

Momentum

Mass in Motion

Momentum is the product of an object’s mass and the object’s velocity.


All matter has mass, so if an object is moving, it has momentum!

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Momentum
Mass in Motion

Momentum Equation

Momentum is the product of an object’s mass and the object’s velocity thus momentum depends on two variables:

1. Mass

2. Velocity

Example 1: Determine the momentum of a 65 kg football player moving west at 3 m/s.

p (momentum) = ?
m (mass) = 65 kg
v (velocity) = 3 m/s, west

Define Variables

Finding velocity

Finding mass

Example 2: Determine the velocity of a 1,500 kg vehicle traveling east with a momentum of 20,000 kg*m/s.

p (momentum) = 20,000 kg*m/s
m (mass) = 1,500 kg
v (velocity) = ?

Define Variables

Momentum
Vector or Scalar?

Momentum is a vector because it has velocity, which is also a vector.

RECALL: Vectors are quantities that have magnitude (size) and direction, and they are often represented by arrows.

Momentum is always defined relative to a frame of reference. For example, imagine a person driving a car while another person is standing by the side of the road watching the car:

• From the perspective of a stationary observer (the person on the side of the road), the car has momentum because it is moving.

• However, from the perspective of the driver, the car has zero momentum because, in the driver's frame of reference, the car is at rest (zero velocity).

Tip: To make problem-solving easier, always assume the frame of reference is stationary unless otherwise stated!

Reference Frames

Practice Problems!

Attempt the problems until you can score an 80% or better.

Multiple Choice

Does a student standing still have momentum?

• Yes

• No

Multiple Choice

You watch a bird flying through the sky. Does the bird have momentum?

• Yes

• No

Multiple Choice

If an object is not moving, there is no momentum.

• True

• False

Fill in the Blanks

Momentum is also known as ____ in _______

Multiple Choice

What is the unit for momentum?

• m/s

• kg/s

• kg

• kg*m/s

Multiple Choice

What is the unit for mass?

• m/s

• kg/s

• kg

• kg*m/s

Multiple Choice

What is the unit for velocity?

• m/s

• kg/s

• kg

• kg*m/s

Fill in the Blanks

The equation to calculate momentum is

Fill in the Blanks

The momentum of an object depends on the objects ____ and _______

Multiple Choice

Momentum is a ______ quantity

• Science

• Scalar

• Vector

• Imaginary

Multiple Choice

A 0.250 kg cart moving at 0.400 m/s has how much momentum?

• 0.1 kg*m/s

• 1 kg*m/s

• 10 kg*m/s

• 100 kg*m/s

Multiple Choice

A 10 kg object is pushed at a speed of 5 m/s. Calculate the momentum of the object. (Include units!)

• 50 m/s

• 50 kg*m/s

• 125 m/s

• 125 kg*m/s

Multiple Choice

Which object listed below has the greatest momentum?

• A 0.05 kg object moving at 0.2 m/s.

• A 0.15 kg object moving at 2 m/s.

• An object with a momentum of 0.79 kg*m/s

• A 0.4 kg object moving at 2 m/s.

Fill in the Blanks

Find the mass of an object with a momentum of 1000 kg*m/s moving at a velocity of 25 m/s. (Include units!)

Fill in the Blanks

Find the velocity of a 50 kg object with a momentum of 850 kg*m/s. (Include units!)