### Slopes - Forces

These slope questions involve forces. You are generally required to draw a force and / or free body diagrams of the forces involved.

This diagram is usually the starting point.

Given - Draw the force diagram for the 5kg mass, showing the components of it's weight.

Diagram 1

Here is the diagram.

Diagram 2
F_{//} is the component of the weight that acts downwards, and parallel to the slope. This is the force that accelerates the mass down the slope.

S is the force exerted by the mass perpendicularly onto the slope. (force of mass on slope)

So what do we do with these two forces?

Study this diagram.

Diagram 3
F_{//}

F_{//} is copied onto the mass itself, and the acceleration can be calculated:

S

The reaction force to S is the force exerted by the slope on the mass called F_{N} = 42,44N.

- F
_{N} is the NORMAL Force.
- A NORMAL Force is the perpendicular force exerted on an object, by the surface on which it is placed.
- Copy S the other way - this would be the force of slope on mass : F
_{N}
- S and F
_{N} are Newton 3 action-reaction forces.

WITH FRICTION

Lets assume that the above question included a friction force of 10N.

Diagram 4
Calculate the magnitude of the acceleration.

Calculate the coefficient of kinetic friction (μ).

This is where the normal force F_{N} is required.

This equation is learnt in Grade 11.You need to know this for your finals.