Rich example

## Suggestion

A particle of mass $\quantity{10}{kg}$ starts at rest on a rough inclined plane. A force of magnitude $\quantity{P}{N}$ is applied to the particle and acts up the slope, parallel to the plane.

When $P = 20$ the particle is on the point of sliding down the plane.

When $P = 40$ the particle is on the point of sliding up the plane.

Can we draw force diagrams that represent these situations?

What do we know about the friction for these two values of $P$?

For each of the following values of $P$ describe how the particle is moving and calculate the frictional force acting on it:

• $P = 25$
• $P = 30$
• $P = 50$

What would a graph of the frictional force against $P$ look like?

What do you know about the particle when $P$ is between the values of $20$ and $40$?