Physics
Work and Energy
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#161 The work done on a body is 49 J in raising it through 2.5 m, the mass of the body is
A) 20 kg
B) 4 kg
C) 2 kg
D) 40 kg
#162 A man pushes a lawn mower with 75 N force directed at an angle of 30° from the vertical. The work done by the man as he cuts a strip of grass 20 m long.
A) 750 J
B) 3750 J
C) 750 J
D) 1500 J
#163 A body of mass 1000 kg traveling at 36 km/h is brought to rest in 50 s. The average retarding force on the body will be
A) 500 N
B) 200 N
C) 250 N
D) 1000 N
#164 Two bodies have same kinetic energy. They are stopped by applying same retarding force. Which body will stop earlier?
A) Lighter one
B) Both will stop simultaneously
C) Heavier one
D) It cannot be predicted
#165 The engine of a car exerts force 2000 N and moves it with a constant velocity of 10 m/s. The power developed by the engine is
A) 20 kW
B) 2000 kW
C) 20 kW
D) 200 kW
#166 One watt-hour equals
A) 3.6×10³ J
B) 3.6×10³ cal
C) 3.6×10^6 J
D) 3.6×10^6 cal
#167 The work done is said to be negative if
A) \(0=0\)
B) \(0=8\)
C) \(0<90^\circ\)
D) \(0>90^\circ\)
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