The situation described involves a ball being released at the top of a slope and rolling down without being pushed. To solve this problem, we need to identify the force that causes the ball to move downhill.
Let's analyze the options given:
- A. Applied Force: This is a force exerted by a person or object when they push or pull another object. In this case, James did not push the ball, so applied force is not the correct answer.
- B. Drag Force: Drag force, also known as air resistance, acts opposite to the direction of an object’s motion through the air. It is not the force causing the ball to move downhill; rather, it would act to slow the ball down.
- C. Friction Force: Friction force acts opposite to the direction of motion between two surfaces in contact. In this case, friction between the ball and the slope would resist the motion of the ball, not cause it to move downhill.
- D. Gravitational Force: Gravitational force is the attractive force exerted by the Earth that pulls objects toward its center. This force pulls the ball downhill when it is released.
- E. Normal Force: The normal force is the perpendicular contact force exerted by a surface on an object resting on it. While the normal force acts on the ball, it acts perpendicular to the slope and does not cause the ball to move downhill.
Given the explanation above, the correct answer is:
D. Gravitational force
Gravitational force is responsible for pulling the ball downhill when it is released from the top of the slope.
