Question

this diagram shows a ball rolling from left to right along a frictionless surface. in which sections will the ball be subjected to a balanced force?
section 1
section 2
section 3
section 4
section 5

a. sections 1 and 4
b. sections 1, 3, and 4
c. sections 2 and 5

Explanation:

To determine when a ball has balanced forces, we use Newton's first law: balanced forces (net force = 0) result in constant velocity (including rest or uniform motion). A frictionless surface means no friction.

• Section 1: The surface is sloped (curved downward). The normal force and gravity are not balanced (there’s a net force along the slope), so the ball accelerates. Forces are unbalanced.
• Section 2: The surface is horizontal (straight, flat). The normal force (upward) balances gravity (downward), and there’s no friction. So net force = 0. Forces are balanced.
• Section 3: The surface is curved upward (a hill). The normal force and gravity combine to create a net centripetal force (toward the center of the curve), so the ball decelerates. Forces are unbalanced.
• Section 4: The surface is sloped (curved downward, like Section 1). There’s a net force along the slope, so the ball accelerates. Forces are unbalanced.
• Section 5: The surface is horizontal (straight, flat), same as Section 2. Normal force balances gravity, no friction. Net force = 0. Forces are balanced.

Thus, Sections 2 and 5 have balanced forces.

Answer:

C. Sections 2 and 5