Question

the force of the ruler on the ball is called an applied force. the force of the barrier on the ball is called a normal force. both of these forces are exerted by surfaces, and the direction of force is at a right angle to the surface. the difference is that an applied force is exerted by a moving object and a normal force is exerted by a stationary object. draw two arrows to represent the applied force and the normal force on the ball.

Explanation:

1. Identify the Ball and Surfaces: The balls are the light blue circles. The ruler (left blue vertical line) and barrier (right blue rectangle) are the surfaces.
2. Applied Force (Ruler on Ball): The ruler is a moving object (or applying force to move the ball). The force direction should be perpendicular to the ruler's surface (horizontal, towards the barrier) since the ruler's surface is vertical. So draw an arrow on one of the balls (e.g., the leftmost ball) pointing to the right (towards the barrier), perpendicular to the ruler's surface.
3. Normal Force (Barrier on Ball): The barrier is stationary. The force direction should be perpendicular to the barrier's surface (horizontal, towards the left) since the barrier's surface is vertical. Draw an arrow on the ball touching the barrier (rightmost ball) pointing to the left, perpendicular to the barrier's surface.
4. Direction and Perpendicularity: Both forces are at right angles to their respective surfaces (ruler and barrier, which are vertical), so the forces are horizontal (perpendicular to vertical surfaces). The applied force pushes the ball towards the barrier, and the normal force from the barrier pushes back (opposing the applied force on the ball in contact with the barrier, or on other balls, the normal force from adjacent surfaces would also be perpendicular, but in this case, the main interaction is ruler - ball (applied) and barrier - ball (normal)).

Answer:

To draw the forces:

• Applied Force (Ruler on Ball): Select the arrow tool. On a ball (e.g., the left - most ball near the ruler), draw an arrow pointing to the right (perpendicular to the ruler’s vertical surface, as the ruler exerts a force to move the ball toward the barrier).
• Normal Force (Barrier on Ball): On the ball touching the barrier (right - most ball), draw an arrow pointing to the left (perpendicular to the barrier’s vertical surface, as the stationary barrier exerts a force opposing the applied force on this ball).

(Note: The actual drawing is done using the arrow tool in the provided interface, with the directions as described above, perpendicular to the respective surfaces and consistent with the definitions of applied (from moving ruler) and normal (from stationary barrier) forces.)