Olympiad Science - Work, Energy and Power
Exam Duration: 45 Mins Total Questions : 30
A ball of mass 1 kg thrown upwards reaches a maximum height of 5 m. Calculate the work done by the force of gravity during this vertical displacement
- (a)
- 30 J
- (b)
- 48 J
- (c)
- 49 J
- (d)
- 59 J
An object of mass 1 kg is raised through a height 'h', Its potential energy is increased by 1 J. Find the height.
- (a)
0.102 m
- (b)
0.105 m
- (c)
0.130 m
- (d)
0.11 0 m
Find the work done by a student in lifting a 0.5 kg book from the ground and keeping it on a shelf of height 1.5 m
- (a)
8.30 J
- (b)
7.35 J
- (c)
5.40 J
- (d)
6.45 J
A block of mass 1 kg slides down on an inclined plane with the angle of inclination of 30°. Find the work done as the block slides through 50 cm.
- (a)
3.45 J
- (b)
5.30 J
- (c)
2.45 J
- (d)
4.50 J
A force of 10 N displaces an object through 20 cm and does the work of 1 J in the process. Find the angle between the force and displacement.
- (a)
Ø = 60°
- (b)
Ø = 50°
- (c)
Ø = 35°
- (d)
Ø = 45°
When a stone tied to a string is whirled in a circle, what kind of work is said to be done on it by the string
- (a)
Positive
- (b)
Negative
- (c)
Zero
- (d)
Undefined
A does 500 J of work in 10 minutes and 8 does 600 J of work in 20 minutes. The power delivered by A and 8 is P1 and P2 respectively. Find the relation between P1 and P2
- (a)
P1 = P2
- (b)
P1 > P2
- (c)
P1 < P2
- (d)
P1 and P2 are undefined
The mass of a body is increased by 100% and velocity of a body is decreased by 50%. What is the percentage change in its kinetic energy?
- (a)
50%
- (b)
50%
- (c)
75%
- (d)
150%
By how much does the kinetic energy of a particle increase if the velocity is increased by a factor of three?
- (a)
6
- (b)
7
- (c)
8
- (d)
9
The heart of a man pumps 4 litres of blood per minute at a pressure of 130 mm of mercu ry.lf the density of mercury is 13.6 g cm-3, calculate the power of the heart.
- (a)
1.144 W
- (b)
2.145 W
- (c)
1.155W
- (d)
3.155 W
A body falling from a height of 10m rebounds from a hard floor. It loses 20% of its energy in the impact. What could be the height to which it would rise after the impact?
- (a)
7 m
- (b)
5 m
- (c)
8 m
- (d)
6 m
A force of 5 N acts on an object. The displacement is perpendicular to the direction of the force. What is the work done?
- (a)
5 J
- (b)
1 J
- (c)
100 J
- (d)
0 J
The kinetic energy of a body is increased by 21%. What is the percentage increase in the linear momentum of the body?
- (a)
20%
- (b)
10%
- (c)
30%
- (d)
5%
If P.E.of the body and the height through which it falls freely are plotted on a graph, it may be noted that the total energy remains the same. Which of the following graphs shows this relation correctly?
- (a)
- (b)
- (c)
- (d)
A block of mass 20 kg is pulled over a smooth inclined plane through 3 m as shown in the figure. The plane makes an angle of 30° with the base. The force applied is parallel to the base. (g= 10ms-2)
Assuming that no energy is lost otherwise, what is the gain in the P.E.of the block
- (a)
30 J
- (b)
20 J
- (c)
300 J
- (d)
600 J
What energy does the person possess while climbing a hill?
- (a)
Only P.E.
- (b)
Only K.E.
- (c)
Only muscular energy
- (d)
Both (A) and (B)
A gun fires a bullet of mass m with velocity v.The mass of the gun is M and it recoils with velocityV. lf the kinetic energy of the bullet is Eb and that of the gun is Eg, identify the relation between Eb and Eg•
- (a)
Eb = Eg
- (b)
Eb< Eg
- (c)
Eb > Eg
- (d)
Eb ≥ Eg
Which of the following is NOT a measure of energy?
- (a)
J s
- (b)
W s
- (c)
kWh
- (d)
erg
An engine can pump 40,000 litresof water to a vertical height of 35 metres in 5 minutes. Calculate the gravitational potential energy of water at the given height.
- (a)
39.2 x 104 J
- (b)
1.4 x 106 J
- (c)
1.37 x 107 J
- (d)
8.5 x 10-3 J
A boy lifts a book of known weight from the surface of a table. To calculate the work done, what does he need to know?
- (a)
The mass of the book
- (b)
The height
- (c)
The cost of the book
- (d)
The time taken by him
A 20 kg ball is thrown upwards with a speed of 6 ms-1. Find the maximum height it reaches (9 = 9.8ms-2).
- (a)
2.86 m
- (b)
1.88 m
- (c)
3.82 m
- (d)
1.84 m
In a factory, due to a sudden strike the work usually done in a day took a longer time. Which of the following happened?
- (a)
Power increased.
- (b)
Power decreased.
- (c)
Energy increased.
- (d)
Energy decreased
A boy moved a body through 3 m in four different ways. In which of the following cases was the work done the maximum
- (a)
Pushing a body over an inclined plane
- (b)
Lifting a body vertically upwards
- (c)
Pushing a body over smooth rollers
- (d)
Pushing on a plane horizontal surface
Work is said to be NOT done when an object moves
- (a)
at an angle of 900 to the direction of the force.
- (b)
at an angle opposite to the direction of the force
- (c)
at any angle to the direction of the force.
- (d)
along the direction of the force
A ball dropped from a 20 m height loses 40 % of its energy on hitting the ground. Upto what height does the ball rebound?
- (a)
28 m
- (b)
8 m
- (c)
12 m
- (d)
20 m
The work done by a man in holding a 15 kg suitcase while waiting for a bus for 45 minutes is
- (a)
675 J.
- (b)
405 J.
- (c)
450 J.
- (d)
zero
Rahul takes 1 minute to raise a box to a height of 1 metre and Rohan takes 1/2 minute to do the same. Which of the following is true of the energy spent by the two?
- (a)
Energy spent by Rahul is more.
- (b)
Energy spent by both Rahul and
Rohan is the same. - (c)
Energy spent by Rohan is more.
- (d)
Energy spent by Rahul is less.
When a force retards the motion of a body, the work done by the force during retardation is
- (a)
zero.
- (b)
negative
- (c)
positive
- (d)
positive or negative depending upon the magnitude of force
Analyse the given statements and choose the correct option.
Statement 1 :The kinetic energy, with any reference, must be positive.
Statement II :The kinetic energy and the square velocity are related.
- (a)
Both statement 1and statement II are correct and statement /I is the correct explanation of statement
- (b)
Both statement 1and statement II are correct, but statement II is not the correct explanation of statement I.
- (c)
Statement 1iscorrect, but statement II is incorrect.
- (d)
Statement 1is incorrect, but statement II is correct.
Rakesh lifts a heavy book from the floor of the room and puts it in the book shelf of height 2 m. In this process, he takes 5 seconds.On which of the following does the work done by him depend
- (a)
Mass of the book and the time taken to do work
- (b)
Weight of the book and the height of the book shelf
- (c)
Height ofthe book shelf and the time taken to do work
- (d)
Mass of the book, height of the book shelf and the time taken to do work