1. Force on an object due to a difference in pressure when immersed in a fluid
The gravitational force on a body
Force resisting the parallel movement of two surfaces in contact
The pulling force exerted by a string, cable, chain or similar object.
Tension
Friction
Upthrust
Weight

2. The Four Fundamental Forces:
Gravitational
Electromagnetic
Strong
Weak

3. Slopes
30/07/2018
LO:
To become confident in resolving vectors in respect to a slope
To use this skill to solve slope problems

4. Forces in static systems:
Friction has a static component which acts parallel to two surfaces and causes them to grip each other
The normal reaction (or contact force) always acts at perpendicular (right angles) to the surface producing it
Weight acts vertically downwards from the centre of gravity

5. Slopes! Weight of the book is 8N Desk is tilted at an angle of 15°
Find the magnitudes of friction and normal reaction for the book at rest on the desk?
Weight of the book is 8N
Desk is tilted at an angle of 15°

6. Sidney is very disappointed when his sledge gets stuck half way down the hill!
If the hill is sloped at an angle of 12° and the combined weight of Sidney and his sledge is 400N, calculate the magnitude of the normal reaction and frictional forces.

7. Complete the Slope Problems Sheet
Then:
Vectors ‘Worksheet’ Qu’s 1-6 & 9

8. Homework Due Mon 4th Oct
Static stick men sheet

9. Normal reaction force always acts at 90° to a surface.
A bit more on reaction…
Normal reaction force always acts at 90° to a surface.
If the surface is smooth this is easy! R
If the surface is rough however, the direction of the reaction depends on where it is on the surface

10. Ladders
For a ladder to stand against a wall , the lines of action of the forces must meet at a point
This can’t happen when you have a smooth wall and a smooth floor
When there is one smooth and one rough surface, there is one position in which the ladder will stand

11. Sidney decides to do some painting!
He places his uniform ladder (10m long and weighing 200N against a smooth wall at an angle of 60°)
Find the reactions of the wall and the ground