All moving objects have momentum. This is a measure of how difficult it is to stop a moving object.

Understand the idea of linear momentum conservation (A)

Understand how momentum can be calculated (C)

Momentum can be calculated using the formula:

**Momentum**

**Objectives**

Know what momentum is (E)

Understand how momentum can be calculated (C)

Understand the idea of linear momentum conservation (A)

**Starter: Which will cause more damage:**

An empty lorry crashing into a house,

or, the same lorry, at the same speed, filled with bricks?

An empty lorry crashing into a house,

or, the same lorry, at the same speed, filled with bricks?

Which has more momentum?

If these two cars have the same mass but one is quicker than the other, which has the most momentum?

The car travelling quicker

If both cars travel at the same velocity, but one is full with luggage and the other is empty, which will have the most momentum?

The heavier car

The bigger an object is and the faster it moves, the more momentum it will have and the more difficult it will be to stop.

mass measured in kg

velocity measured in m/s

momentum measured in kgm/s

Try it out....

Complete the momentum worksheet

Answers

1 a) 600 kg m/s, b) 24 000 kg m/s, c) 100 million kg m/s, d) 24 million kg m/s.

2 a) 180 kg m/s.

3 a) 24 000 kg m/s.

c) i) 48 000 J, ii) 36 000 J.

d) Some of the kinetic energy was transformed into sound and heat energy in the collision.

Can you prove momentum conservation exists?

Using the following equipment can you prove the conservation of linear momentum?

Newton trolleys

Masses

Blocks (to prevent the trolleys going too far)

Timers

Metre rules

Help:

Follow the "investigating a controlled explosion" worksheet

Stretch:

Can you prove that this is the case in 2D

Useful equations

When calculating momentum, consider the situation before and after.

Before

m1, u1

m2, u2

after

Total momentum =

Conservation of momentum says: total before = total after

Total momentum =

Complete the Explosions worksheet

Plenary

True or false

1. An object's momentum is the same as its velocity.

2. Momentum is a vector quantity.

3. Momentum is determined by an objects mass and velocity.

4. An explosion can demonstrate the principle of momentum conservation.

5. Momentum is never conserved in collisions.

6. When two objects interact in a closed system, their momentum is conserved.

1. False

2. True

3. True

4. True

5. False

6. True

**Homework**

**Complete the extended essay "Energy and momentum"**

Extension questions

1. A bullet of mass 10g is fired from a 6kg rifle at a speed of 300m/s. What is the recoil velocity of the rifle?

2. A smart car of mass 500kg has a head on collision with a new mini of mass 1000kg travelling at 20m/s.. Both cars stop dead. How fast was the mini travelling?

Momentum before firing = 0

Momentum after firing= 0

v= 0.5m/s

= 3 - 6v=0

= 0.010 × 300 + 6 ×(-v)

Momentum of bullet + momentum of rifle

Total momentum after collision=0

Since

Try these...

1. An American football player has a mass of 100 kg and runs at 8m/s towards another player. What is his momentum?

2. A Basketball has a mass of 2kg, if thrown with a speed of 25 m/s, what is its momentum?

1. 100 kg x 8 m/s = 800 kgm/s

2. 2kg x 25 m/s = 50 kgm/s

Total momentum before collision

v= 40m/s

For a collision

For an explosion

Total momentum = 0

Total momentum = 0

m1, v1

m2, v2

Before

After