PREVIOUS YEAR QUESTION CHAPTER – 2
WORK ENERGY POWER
2025
1.
Which among the
following is a vector quantity?
(a)
work (b) energy
(c) power (d) moment of couple
2.
What is the
correct energy transformation during burning of a candle? (a) heat → kinetic +
potential (c) chemical → heat + light
Answer
(b)
heat → chemical +
light (d) mechanical → chemical + heat
3.
Richa weighing 40
kgf leaves point P on her skateboard and reaches point Q on the ground with
velocity 10 ms–1. Calculate:
(a) The kinetic energy of Richa at point Q.
(b) The vertical height of point P above the ground.
(Use g as 10 m/s2 and neglect friction)
(c) The kinetic energy of Richa at point R. (While
moving from Q to R, she loses 500 J of energy against friction.)
2024
4.
When a bell fixed
on a cycle rings, then the energy conversion that takes place is:
(a) gravitational potential energy to sound energy
(b) kinetic energy to sound energy
(c) sound energy to electrical energy
(d) sound energy to mechanical energy
5.
A force ‘F’ moves
a load from A to C as shown in the figure below. For the calculation of the
work done, which of these lengths would you use as the displacement?
(a) 4m (b) 5m
(c) 7m (d) 3 m
6.
Sumit does 600 J
of work in 10 min and Amit does 300 J of work in 20 min. Calculate the ratio of
the powers delivered by them.
7.
Two identical
marbles A and B are rolled down along Path 1 and Path 2 respectively. Path 1 is
frictionless and Path 2 is rough.
(a) Which marble will surely reach the next peak?
(b) Along which path/s the mechanical energy will be
conserved?
(c) Along which path/s is the law of conservation of
energy obeyed?
2023
8.
When the speed of
a moving object is doubled, then its kinetic energy: (a) remains the same (b)
decreases (c) is doubled (d) becomes four times
9.
The energy
conversion in a washing machine is from __________.
(a) magnetic to electrical (b) electrical to
mechanical
(c) electrical to magnetic (d) magnetic to electrical
10. What should be the angle between the direction of
force and the direction of displacement, for work to be negative?
11. Name the physical quantity obtained using the formula 𝑈/ℎ where U is the
potential energy and h is the height.
12. Calculate the power spent by a crane while lifting a
load of mass 2000 kg, at velocity of 1.5 ms-1. (g = 10 ms-2)
13. A car of mass 120 kg is moving at a speed 18 km/h and
it accelerates to attain a speed of 54 km/h in 5 seconds. Calculate: (a) the
work done by the engine. (b) the power of the engine.
2020
14. Define a kilowatt hour. How is it related to joule?
15. A satellite revolves around a planet in a circular
orbit. What is the work done by the satellite at any instant? Give a reason.
16. Give one example of each when:
(i)
Chemical energy
changes into electrical energy.
(ii)
(ii) Electrical
energy changes into sound energy.
17. A crane ‘A’ lifts a heavy load in 5 seconds, whereas
another crane ‘B’ does the same work in 2 seconds. Compare the power of crane
‘A’ to that of crane ‘B’
18. The figure below shows a simple pendulum of mass 200
g. It is displaced from the mean position A to the extreme position B. The
potential energy at the position A is zero. At the position B the pendulum bob
is raised by 5 m.
(i)
What is the
potential energy of the pendulum at the position B?
(ii)
What is the total
mechanical energy at point C?
(iii)
What is the speed
of the bob at the position A when released from B? (Take g = 10 ms-2
and there is no loss of energy.)
2019
19. Two bodies A and B have masses in the ratio 5:1 and
their kinetic energies are in the ratio 125:9. Find the ratio of their
velocities.
20. (i) Name the physical quantity which is measured in
calories. (ii) How is calorie related to the S.I unit of that quantity?
21. A body of mass 10 Kg is kept at a height of 5 m. It is
allowed to fall and reach the ground.
(i)
What is the total
mechanical energy possessed by the body at the height of 2 m assuming it is a
frictionless medium?
(ii)
What is the
kinetic energy possessed by the body just before hitting the ground? Take g =
10 m/s2.
2018
22. (i) State and define the S.I. unit of power. (ii) How
is the unit horse power related to the S.I. unit of power?
23. State the energy changes in the following cases while
in use: (i) An electric iron. (ii) A ceiling fan.
24. A force acts on a body and displaces it by a distance
S in a direction at an angle θ with the direction of force. What should be the
value of q to get the maximum positive work?
2017
25. If the power of a motor be 100 kW, at what speed can
it raise a load of 50,000 N?
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