PG TRB Physics Previous Year Questions with Answer Key - 5

Question: 21

To hear a clear echo, the minimum distance should be

(A) 165 feet

(B) 165 meter

(C) 16.5 feet

(D) 16.5 meter

Question: 22

A planet is moving around the sun in an elliptical orbit. Its speed is

(A) maximum when it is nearest to the sun

(B) maximum when it is farthest from the sun

(C) same at all points of the orbit

(D) none of the above

Question: 23

The Carnot’s engine takes heat

(A) at constant energy

(B) at constant volume

(C) at constant temperature

(D) at constant pressure

Question: 24

Which one of the following is the unit of activity of a radioactive source?

(A) Tesla

(B) Lux

(C) Siemens

(D) Becquerel

Question: 25

Kerosene oil rises up in a wick of a lantern because of

(A) Diffusion of the oil through the wick

(B) Surface tension

(C) Buoyant force of air

(D) The gravitational pull of the wick