The same sealed equipment case is placed, at different times, on two sections of a sloping river bank. Both sections slope at the same angle, but their surfaces are different. The case is not tied to anything, and on each section it is released from rest.
Three forces, P, Q and R, act on the case. P acts vertically downwards, Q acts at right angles to the bank and away from its surface, and R acts up the bank.
The table gives information about these forces immediately after the case is released on each section.
| force or component | section 1 | section 2 |
|---|---|---|
| component of P perpendicular to the bank, into the surface | 240 N | 240 N |
| Q | 240 N | 240 N |
| component of P parallel to the bank, down the slope | 180 N | 180 N |
| R | 180 N | 100 N |
Explain what forces P, Q and R represent, including whether each force is a contact force or a non-contact force.
Use the information in the table to explain what happens to the case on each section of the bank.