Q: A body of mass m kg is lifted by a man to a height of one metre in 30 seconds. Another man lifts the same mass to the same height in 60 seconds. The work done by them are in the ratio
a)1:2
b)1:1
c)2:1
d)4:1
Answer: (b) 1:1
Q: Which of the following is a scalar quantity
a)Displacement
b)Electric field
c)Acceleration
d)Work
Answer: (d) Work
Q: A force of 5 N acts on a 15 kg body initially at rest. The work done by the force during the first second of motion of the body is
a)5 J
b)⅚ J
c)6 J
d)75 J
Answer: (b) ⅚ J
Q: A force of 5 N, making an angle θ with the horizontal, acting on an object displaces it by 0.4 m along the horizontal direction. If the object gains kinetic energy of 1 J, the horizontal component of the force is
a)1.5 N
b)2.5 N
c)3.5 N
d)4.5 N
Answer: (b) 2.5 N
Q: The work done against gravity in taking 10 kg mass at 1 m height in 1 sec will be
a)49 J
b)98 J
c)196 J
d)None of these
Answer: (b) 98 J
Q: A body of mass 6 kg is under a force which causes displacement in it is given by S = t2/4 mts where t is time. The work done by the force in 2 seconds is
a)12 J
b)9 J
c)6 J
d)3 J
Answer: (d) 3 J
Q: If the unit of force and length each be increased by four times, then the unit of energy is increased by
a)16 times
b)8 times
c)2 times
d)4 times
Answer: (a) 16 times
Q: A man pushes a wall and fails to displace it. He does
a)Negative work
b)Positive but not maximum work
c)No work at all
d)Maximum work
Answer: (c)No work at all
Q: When a retarding force is applied to stop a train, the train stops after 80 m. If the speed is doubled, then for the same retarding force, the distance when the train stops would be
a)The same
b)Doubled
c)Halved
d)Four times
Answer: (d) Four times
Q: You lift a heavy book from the floor of the room and keep it in the bookshelf having a height of 2 m. This process takes 5 seconds. The work done by you will depend on
a)Mass of the book and the time taken
b)Weight of the book and height of the bookshelf
c)Height of the bookshelf and the time taken
d)Mass of the book, height of the bookshelf and the time taken
Answer: (b) Weight of the book and height of the bookshelf
