1. starter
My mass is about 75 kg. When I climb my stairs, I rise vertically by 3 metres.
What is my weight (in newtons)?
750 N
How much gravitational potential energy do I gain?
2250 J

2. Momentum L.O. Calculate the momentum of a moving object.
To use the conservation of momentum to calculate the mass, velocity or momentum of a body involved in a collision or explosion.
Homework: Kinetic Energy and Basic Momentum Calculations worksheet

3. Homework: Kinetic Energy and Basic Momentum Calculations worksheet

4. How will the truck and car move after they crash into each other?

5. The momentum of an object = its mass x its velocity

7. Use a calculator to work out the momentum in each of these cases:
Jack has a mass of 50 kg and runs with velocity 8 m/s.
A truck of mass kg is travelling at 18 m/s (40 mph).
A car of mass 1000 kg is travelling at 31.6 m/s (70 mph).
A train with a mass of kg has a velocity of 40 m/s (about 90 mph).
The Earth has a mass of 6  1024 kg and is moving around the Sun with a velocity of m/s (about mph). Calculate the Earth’s momentum.
A crash report says ‘The train had a momentum of kg m/s.’ If the train had a mass of kg, what was its velocity?
Ap 4.17

8. Investigating collisions
Investigating collisions. Work out the momentum of the objects before and after the collision. Remember momentum have a direction as well as size.

10. Momentum is conserved whenever objects interact, provided no external forces act on them.

11. To do: Workbook page 70

12. Momentum L.O. Calculate the momentum of a moving object.
To use the conservation of momentum to calculate the mass, velocity or momentum of a body involved in a collision or explosion.
Homework: Kinetic Energy and Basic Momentum Calculations worksheet

13. Marking Homework 1a) KE = ½mv2 = ½ x (400) x (15)2 = 45,000 J
1b) Momentum = mv = (400) x (15) = 6,000 kgm/s
2a) KE = ½mv2 = 1248 J
2b) Reduced by a quarter as KE is proportional to v2.
2c) Momentum = mv = 312 kgm/s

14. Marking Homework 3a) 3b) Momentum =mv = 70x5 = 350 kgm/s
3c) Momentum =mv = -50x5= -350 kgm/s
3d) 350 – 350 = 0
5 m/s
7 m/s
50 kg
70 kg

15. Marking Homework 4a) 60,000 kgm/s 4b) 900,000 J 4c) 0 kgm/s 4d) 0 J
4e) 60,000 kgm/s
4f) 900,000 J
4g) 40,000 kgm/s
4h) 400,000 J
Before the crash:
30 m/s
0 m/s
After the crash:
20 m/s
20 m/s

16. Marking Homework 4i) 20,000 kgm/s 4j) 200,000 J
Before the crash:
30 m/s
4i) 20,000 kgm/s
4j) 200,000 J
4k) 40, , = 60,000 kgm/s
4l) 400, , = 600,000 J
4m) The same
4n) Lost as heat + sound and changed into elastic potential energy in the deformed metal.
0 m/s
After the crash:
20 m/s
20 m/s