Question

During the swing of a frictionless pendulum, what energy form(s) remain constant?

1) kinetic energy only
2) potential energy only
3) both kinetic energy and potential energy
4) kinetic plus potential energy
5) None of these forms remains constant.

Answer 1

The kinetic energy and potential energy of a frictionless pendulum change throughout its swing, but the total mechanical energy (kinetic plus potential) remains constant due to conservation of energy.

Step-by-step explanation:

During the swing of a frictionless pendulum, the kinetic plus potential energy remain constant. This concept relates to the conservation of mechanical energy in the absence of dissipative forces such as friction. Specifically:

• At the moment the pendulum is at its highest point, just before falling back (point i.), it has maximum potential energy and minimal kinetic energy.
• At the midpoint between the two ends (point ii.), the pendulum has its maximum kinetic energy and lower potential energy.
• Just before reaching the end of the swing (point iii.), the pendulum's kinetic energy decreases as it is converted back into potential energy.

The sum of kinetic energy and potential energy is conserved throughout the motion, aligning with the principle of conservation of mechanical energy for a harmonic oscillator.