Question

Simple Pendulum with Gravity

A pendulum consists of a mass m = 0.08 kg hanging from a flexible string of length L. The string is very thin, very light, and does not stretch. It makes small oscillations, with a period of 0.622 s.

What is the oscillation frequency of the pendulum? Neglect any air resistance.

What would the period of the pendulum be on the moon's surface?

Indicate for each of the following statements whether it is correct or incorrect.
Correc/tIncorrect The force of gravity acts upward on the mass.
Correct/Incorrect The tension acts on the mass along the string, toward the hanging point.
Correct/Incorrect The tension does no work at any time during an oscillation.
Correct/Incorrect The sum `kinetic energy + potential energy' of the mass is constant during an oscillation.

Answer 1

given

m = 0.08 kg
T = 0.622 s

a) The oscillation frequency of the pendulum = 1/T

= 1/0.662

= 1.51 Hz

b) T_moon/T_earth = sqrt(g_earth/g_moon)

T_moon = T_earth*sqrt(g_earth/g_moon)

= 0.622*sqrt(9.8/1.6)

= 1.54 s

c)

Incorrect : The force of gravity acts upward on the mass.
Correct: The tension acts on the mass along the string, toward the hanging point.
Correct: The tension does no work at any time during an oscillation.
Correct: The sum `kinetic energy + potential energy' of the mass is constant during an oscillation.