Question

A block moves along a table at a constant velocity and then rolls off the edge of the table. The forces that should be included in a free body diagram for the ball as it falls to the ground are:

normal force from table
friction force from table
gravity
force of fall

Answer 1

Gravity

Step-by-step explanation:

When the ball is falling to the ground, there is only one force- gravity. In some cases, there may be air resistance, but that seems to be neglected here.

Normal force:

Cannot be included. Normal force is only applicable when object is on a surface, and it acts perpendicular to the surface. Since the ball is falling, there is no surface, and therefore no normal force. This question gives you unnecessary information, designed to trick you. Please remember when normal force is applicable.

Friction force:

Also only applicable when object is moving, and is on the table. Friction only applies when there is an applied force. There is no applied force when the ball is falling, so therefore no friction force.

Force of fall:

First of all, what is this? There is nothing called force of fall.

Gravity:

This is the only one that applies. Just draw a vector arrow from the bottom of the ball and label it mg (acceleration due to gravity).