A Cyberphysics Page

Simple Harmonic Motion - Multiple Choice Questions

Q20. Two pendulums, P and Q, are set up alongside each other. The period of P is 1.90 s and the period of Q is 1.95 s.

How many oscillations are made by pendulum Q between two consecutive instants when P and Q move in phase with each other?

A 19

B 38

C 39

D 78

The difference in time period is 0.05s - therefore to make up a complete extra swing P will move one more period than Q does in the same time.

Let number of swings of Q = n

Then n x 1.95 = (n+1) x 1.90

1.95n = 1.90n + 1.90

0.05n = 1.90

n = 38 - choice B