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Year 11
Edexcel
Higher

Conservation of momentum

I can use the principle of conservation of momentum to calculate motions after a collision or explosion.

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New
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Year 11
Edexcel
Higher

Conservation of momentum

I can use the principle of conservation of momentum to calculate motions after a collision or explosion.

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Lesson details

Key learning points

  1. Momentum = mass × velocity, p = mv
  2. In a closed system, the total momentum before an event equals the total momentum after the event.

Keywords

  • Momentum - is the product of the mass and velocity of an object, p = m × v

  • Kilogram metres per second - is the unit of momentum (kg m/s)

  • Conservation of momentum - is the principle that states, for a closed system, momentum is always conserved in any interaction

  • Collisions - happen when two objects move together and hit each other

  • Explosions - happen when a single object splits, or combined objects separate, into pieces that move apart

Common misconception

Pupils may assume that being able to complete calculations by substituting numbers into an equation is the same as fully understanding the relationship.

Include questions for which pupils are required to explain their understanding.

It can be helpful for pupils to observe how momentum is conserved in a collision or explosion. The most straightforward way is to use the spring loaded trigger in a dynamics trolley to cause stationary trolleys to move in opposite directions, and stack different numbers of trolleys on each side.
Teacher tip

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

Lesson video

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Starter quiz

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6 Questions

Q1.
Which of the following terms means the highest velocity of an object falling through a fluid?
top velocity
ultimate velocity
Correct answer: terminal velocity
final velocity
Q2.
Which of the following will reduce the total stopping distance of a vehicle?
higher speed
wet roads
alcohol consumption
icy roads
Correct answer: increased driver concentration
Q3.
What size resultant force will cause an object of mass 6.0 kg to accelerate at 20 m/s$$^2$$?
0.3 N
3.3 N
14 N
26 N
Correct answer: 120 N
Q4.
Which of the following relationships can be used to find the acceleration $$a$$ of an object with mass $$m$$ when there is a resultant force $$F$$ acting on it?
$$a = F × m$$
$$a = F + m$$
$$a = F - m$$
Correct answer: $$a= \frac{F}{m}$$
$$a = \frac{m}{F}$$
Q5.
A scooter and rider have a combined mass of 150 kg. Calculate their acceleration when a resultant force of 450 N acts on them.
0.33 m/s$$^2$$
Correct answer: 3.0 m/s$$^2$$
6.0 m/s$$^2$$
300 m/s$$^2$$
600 m/s$$^2$$
Q6.
A stone of mass 0.5 kg is falling through the air. It has a weight of 5 N and a drag force of 4 N acting upwards on it. Calculate the acceleration of the stone. You do not need to include the unit.
Correct Answer: 2, 2.0, 2.00

Exit quiz

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6 Questions

Q1.
Match the following key terms to their definition.
Correct Answer:momentum,the product of the mass and velocity of an object, $$p = m × v$$

the product of the mass and velocity of an object, $$p = m × v$$

Correct Answer:kilogram metres per second (kg m/s),the unit of momentum

the unit of momentum

Correct Answer:conservation of momentum,for a closed system, momentum is always conserved in any interaction

for a closed system, momentum is always conserved in any interaction

Correct Answer:collisions,happen when two objects move together and hit each other

happen when two objects move together and hit each other

Correct Answer:explosions,happen when a single object splits into pieces that move apart

happen when a single object splits into pieces that move apart

Q2.
Starting with the smallest momentum, sort the following objects into order of increasing momentum.
1 - a lorry stationary of mass 3000 kg
2 - a motorcycle of mass 200 kg travelling at 20 m/s
3 - a van of mass 1200 kg travelling at 10 m/s
4 - a car of mass 800 kg travelling at 16 m/s
Q3.
Which of the following is always correct for a closed system of objects that interact with each other?
Total momentum increases in explosion interactions.
Total momentum decreases in any collision interactions.
Correct answer: Total momentum is always the same before and after any interaction.
Total momentum decreases in explosion interactions.
Total momentum increases in any collision interactions.
Q4.
A toy aeroplane of mass 1.5 kg has a momentum of 30 kg m/s. Calculate the velocity of the aeroplane.
0.05 m/s
Correct answer: 20 m/s
28.5 m/s
31.5 m/s
45 m/s
Q5.
Two stationary dynamics trolleys are separated by an explosion. Trolley A (mass = 1.5 kg) travels at 3.0 m/s after the explosion. Calculate the speed of trolley B (mass = 0.5 kg) after the explosion.
Correct Answer: 9.0 m/s, -9.0 m/s, -9 m/s, 9 m/s
Q6.
A van (mass = 1600 kg) travelling at 5.0 m/s collides with a stationary car (mass = 900 kg) and they join together. Calculate the velocity at which they move off after the collision.
8.8 m/s
5.0 m/s
Correct answer: 3.2 m/s
1.7 m/s
0 m/s