How to calculate momentum 

This lesson will show you how to calculate momentum using the mass and velocity.


Does it make sense though why we need the mass and the velocity?

Look at the two vehicles above and tell me which vehicle will require more effort to stop?

A 2500 pounds car moving 50 miles per hour or a 20,000 pounds truck moving 50 miles per hour.

It will be harder to stop the truck, so we say that the truck has more momentum. Thus, momentum depends on the mass.

What about the velocity?

Which vehicle will require more effort to stop?

A 2500 pounds car moving 5 miles per hour or a 2500 pounds car moving 90 miles per hour.

It will be harder to stop the 2500 pounds car moving 90 miles per hour, so we say that the car with the greater velocity has more momentum. Momentum thus depends also on the velocity. 

How to calculate momentum: Here is the Formula!

Definition of momentum:

The momentum of an object is the product of the mass and the velocity. 

momentum = mass × velocity

momentum = mv

When direction is not important, we can use instead the following formula.

momentum = mass × speed = mv

Notice that we still use v as an abbreviation for the velocity or the speed when direction is important or not.

Resist the urge though to think that mass has more bearing on the momentum. 

It is quite possible that a bicycle can have more momentum than a truck.

A bike weighing 40 pounds moving with a speed of 30 miles per hour will have more momentum than a truck moving 5 miles per hour.

An object at rest has no momentum because it has no speed even though the mass is still there.

It is easy to see. Since v = 0, momentum  = m times 0 = 0  

The concept of momentum applies only to moving objects. It is basically inertia in motion.

However, once an object is in motion, both mass and speed are taken into account.

From what we have seen so far, you may have realized that a moving object can have a large momentum if either the mass or the speed is large or both. 

Unit of momentum: The mass is expressed in kg and the velocity can be expressed in m/s

The momentum is thus expressed in kg.m/s

This lesson on how to calculate momentum is over. 

Momentum quiz

Take the momentum quiz below to see how well you understand momentum. After completing this quiz with 100% accuracy, you will know exactly what the momentum is. You will not need to use a paper and pencil to complete this quiz.

First, read this lesson about momentum and then take this quiz.

Objective of the momentum quiz:

  • Know what the unit of momentum is
  • Know how to use the formula to find the momentum
  • Identify real life situations of momentum
Test your knowledge with the quiz below:

1. The momentum depends on the

weight and acceleration
mass and acceleration
weight and speed
mass and velocity.

2. The formula to get the momentum is

momentum = w*v
momentum = m*v
momentum = m*a
momentum = w*a.

3. Which vehicle has greater momentum? A truck at rest or a man walking 3 miles per hour

The man
The truck
Neither has greater momentum
The question does not make sense

4. If an object has no momentum, the possible cause could be because

the mass is zero
the object is moving but not accelerating.
the velocity is zero
None of the above

5. The unit of momentum is


6. The momentum of a 1000 grams object moving with a speed of 20 meters per second is

2000 kg.m/s
20000 g.m/s
20 kg.m/s
200 g.m/s

7. Which vehicle has a smaller momentum? A 2000 pounds car moving at 30 m/s or a 4000 pounds light truck moving at 15 m/s?

The truck has a smaller momentum
They have the same momentum
The car has a smaller momentum
The momentum cannot be computed with the information that is given

8. Which statement is true?

Once an object is in motion, the momentum is constant
Atoms are too tiny to have momentum
When a vehicle is not accelerating, the momentum will decrease.
The mass is constant

9. Two 747 airplanes cruise with the same speed of 500 miles per hour. Do they airplane have the same momentum?

They do since they have the same mass and speed
Airplanes can never ever have the same momentum
Nonsense question
Not enough information

10. Which sport momentum is really important?

Ping Pong

Score =

I strongly recommend you try your very best to complete this series circuit quiz on your own. Resist the urge to see the answers. Review the lesson about series circuit again. However, if you still cannot get 100% on your own, click here to see the answers.

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