September 20, 2022
In this chapter of AS/A-level Physics, you will learn about Force and Motion.
Force and Motion
Gravitational force:
- When it comes to AS/A-level Physics, Mass is the amount of matter you contain à measured in kilograms (Kg)
- Weight is the force of gravity pulling you down à measured in newton’s (N)
- Ideal friction – actual friction = [amount] friction
Pressure
Pressure is Force per unit area in AS/A-level Physics.
pressure = Force (N)/ Area (m2)
E.g.:
A man can safely lie on a bed of nails by spreading his weight over 750 nails. Man weighs 600N and the area of each nail is 8x10-6. Calculate the average pressure on each nail.
Average weight acting on each nail:
= 600 / 750 = 0.8N
Therefore, the average weight acting on each nail is around 0.8𝑁 𝑝𝑒𝑟 𝑛𝑎𝑖𝑙
Average pressure acting on the man will be:
= 0.8 / 8x10-6 = 1 x 105 Pa
1 x 105 Pa is so small that the man will not get hurt.
Floating and sinking
- Ocean liners float due to the huge amount of water that their hulls displace.
- If an object floats, up thrust = weight
- If an object sinks, up thrust < weight.
- When an object is completely or partly immersed in a fluid, it experiences an up thrust equal to the weight of the fluid displaced in AS/A-level Physics.
Good. You now can handle some concept on Force and Motion in AS/A-level Physics.