Momentum
Momentum is the tendency of an object to keep moving, or to stop the object from moving.
Momentum is a vector quantity.
Example calculations.
1.A stone of mass 0.2kg is moving through the air at a velocity of 4m/s in the forward direction. Calculate the momentum of the stone.
Momentum = mass x velocity
Momentum = 0.2kg x 4m/s = 0.8 kg m/s
2. A ping pong ball of mass 3g is moving forward at a velocity of 6m/s. Calculate the momentum of the ping pong ball.
Convert 3g into kg, 3g = 0.003kg
Momentum = mass x velocity
Momentum = 0.003kg x 6m/s = 0.018 kg m/s
3. A boulder of mass 20kg is rolling down a hill with a momentum of 200kgm/s. Calculate the velocity of the boulder.
Velocity = momentum/mass
Velocity = 200/20 = 10m/s
Momentum as a vector quantity
Momentum is a vector quantity, so it has both a magnitude and direction.
The magnitide is the size of the momentum e.g. 1kg m/s or 10 kg m/s
In the diagram below the cannon ball has a forward velocity, so it will have a + momentum. The cannon has a backwards recoil velocity, so it has a – momentum.
Practice Question
1. State the formula for momentum when each of the following is the subject
1a. Momentum =
1b. Velocity =
1c. Mass =
2.A 3 kg object moves with a velocity of 2.5 m/s. Calculate its momentum.
3.An object has a momentum of 24 kg m/s and a mass of 6 kg. Calculate its velocity.
4. An object traveling at 15 m/s has a momentum of 75 kg m/s. What is its mass?
5. A 10-tonne lorry moves at a velocity of 25 m/s. Calculate its momentum. (1 tonne = 1,000 kg)
6.A mass of 200 g is moving at 15 m/s. Calculate its momentum. (Convert mass to kg)
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Accordion Content
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