Question

4.16 q: a 1.0 - newton metal disk rests on an index card that is balanced on top of a glass. what is the net force acting on the disk? (a) 1 n (b) 2 n (c) 0 n (d) 9.8 n 8 q: which body is in equilibrium? (a) a satellite orbiting earth in a circular orbit (b) a ball falling freely toward the surface of earth (c) a car moving with constant speed along a straight, level road (d) a projectile at the highest point in its trajectory

Explanation:

4.16 Q1

Step1: Analyze forces on disk

The metal disk is at rest. According to Newton's first - law, when an object is at rest, the net force acting on it is zero. The gravitational force of 1.0 N acting downwards is balanced by the normal force exerted by the index card acting upwards.

Step1: Recall equilibrium condition

An object is in equilibrium when the net force acting on it is zero and its acceleration is zero.

Step2: Analyze each option

• Option A: A satellite in circular orbit has a centripetal force acting on it, so it is not in equilibrium.
• Option B: A ball falling freely has a non - zero acceleration due to gravity, so it is not in equilibrium.
• Option C: A car moving with a constant speed along a straight, level road has zero acceleration. The forces acting on it (such as the driving force and friction) are balanced. So it is in equilibrium.
• Option D: A projectile at the highest point in its trajectory still has a non - zero acceleration (acceleration due to gravity), so it is not in equilibrium.

Answer:

C. 0 N

8 Q