Figure 1.4

A block slides on a rigid plane.

When the user checks the appropriate option:

• GRAVITY is shown in green, acting at the center of mass
• APPLIED FORCE is shown in pink, acting at the center of mass.

If the user chooses, the block can be separated from the plane. The block will become transparent.

• FRICTION is shown in blue on both the block and plane.
• NORMAL is shown in red on both the block and plane