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

---