Question

A seconds pendulum is mounted in a rocket. Its
period of oscillation decreases when the rocket
(a) comes down with uniform acceleration
(b) moves round the earth in a geostationary
orbit
(c) moves up with a uniform velocity
(d) moves up with uniform acceleration

Answer 1

Answer:Correct answer= B

As the rocket accelerates upwards, pseudo force acts in the opposite direction of propagation.

=> Pseudo force acts in downward direction and gets added up to gravitational force.

=> Effective gravity= gravitational force+ pseudo force

                               >Gravitational force

=>             g'        >         g       where g' = effective gravity

Since time period of oscillation of pendulum= √(L/g)

      where L= length of the pendulum

                  g= gravitational force acting on the pendulum

=> In this situation,

         time period of oscillation of pendulum=√(L/g')

Since g' > g

=>     √(L/g')      <     √(L/g)

=>  Time period of oscillation decreases