253. A machine is said to be irreversible if its efficiency is

A.100%

B.Less than 50%

C.0%

D.More than 50%

254. Pick up the incorrect statement from the following. In case of a suspension bridge if there is a rise in temperature

A.The dip of the cable will increase

B.The length of the cable will increase

C.The dip of the cable will decrease

D.All of the above

255. If the speed of rotation of earth decreases, the weight of the body will

A.Increase

B.Decrease

C.Remain same

D.Increase/decrease depending on range of increase

256. Two cars are 10 km apart and moving in the same direction at speed of 40 km/hr. A car moving in opposite direction meets these cars at interval of 8 minutes. At what speed the other car is moving

A.75 km/hr

B.60 km/hr

C.45 km/hr

D.35 km/hr

257. The friction experienced by a body, when in motion, is known as

A.rolling friction

B.dynamic friction

C.limiting friction

D.static friction

258. Two balls of equal mass and of perfectly elastic material are lying on the floor. One of the ball with velocity v is made to struck the second ball. Both the balls after impact will move with a velocity

A.v

B.v/2

C.v/4

D.v/8

259. The velocity ratio in case of an inclined plane inclined at angle θ to the horizontal and weight being pulled up the inclined plane by vertical effort is

A.sin θ

B.cos θ

C.tan θ

D.cosec θ

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