WORK AND ENERGY
Multiple Choice Questions
Q. A car is accelerated on a levelled road and attains a velocity 4 times of its
initial velocity. In this process the potential energy of the car
(a) does not change
(b) becomes twice to that of initial
(c) becomes 4 times that of initial
(d) becomes 16 times that of initial
Q. In the case of negative work the angle between the force and displacement is
(a) 0∘
(b) 45∘
(c) 90∘
(d ) 180∘
Questions
Q. A porter lifts a luggage of 15
kg from the ground and puts it on his
head 1.5 m above the ground. Calculate
the work done by him on the luggage.
Q. A pair of bullocks exerts a force
of 140 N on a plough. The field
being ploughed is 15 m long.
How much work is done in
ploughing the length of the field?
Q. What is the work to be done
to increase the velocity of a car from 30kmh–1 to 60kmh–1 if the mass of
the car is 1500 kg?
Q. The kinetic energy of an object of
mass, m moving with a velocity
of 5ms–1 is 25 J. What will be its
kinetic energy when its velocity
is doubled? What will be its
kinetic energy when its velocity
is increased three times?
Q. Find the energy possessed
by an object of mass 10 kg when it is at
a height of 6 m above the ground. Given, g=9.8ms–2 .
Q. An object of mass 12 kg is
at a certain height above the ground.
If the potential energy of the object is
480 J, find the height at which the
object is with respect to the ground.
Given, g=10ms–2 .
Q. Two girls, each of weight 400
N climb up a rope through a height of 8
m. We name one of the girls A and the
other B. Girl A takes 20 s while B takes
50 s to accomplish this task. What is the
power expended by each girl?
Q. An electric bulb of 60 W is
used for 6 h per day. Calculate the ‘units’
of energy consumed in one day by the
bulb.
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