Question

10. As a simple pendulum swings back and forth, the forces acting on the suspended object are the gravitational force, the tension in the supporting cord, and air resistance. (a) Which of these forces, if any, does no work on the pendulum? (b) Which of these forces does negative work at all times during its motion? (c) Describe the work done by the gravitational force while the pendulum is swinging.​

Answer 1

Hey there! It looks like you’re asking about the forces acting on a simple pendulum. Here’s what I know:

(a) The tension in the supporting cord does no work on the pendulum because the force is always perpendicular to the direction of motion.

(b) Air resistance does negative work at all times during the pendulum’s motion because it always opposes the motion.

© The work done by the gravitational force while the pendulum is swinging depends on the position of the pendulum. When the pendulum is at its highest point, the gravitational force does no work because it is perpendicular to the direction of motion. As the pendulum swings downward, the gravitational force does positive work because it is in the same direction as the motion. When the pendulum reaches its lowest point and starts to swing upward, the gravitational force does negative work because it opposes the motion.

Answer 2

(i) Answer (b). Tension is perpendicular to the motion. (ii) Answer (c). Air resistance is opposite to the motion.