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
Find the kinetic energy of a ball of mass 200 g moving at a speed of 20 cm s-1
- (a)
0.4 J
- (b)
0.004 J
- (c)
0.001 J
- (d)
0.1 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 body of mass 0.5 kg is taken to a height Re above the earth's surface, where Re is the radius of the earth. If the body is now raised through a height of 2 m, what is the increase in its potential energy?
- (a)
0.25 J
- (b)
0.50 J
- (c)
0.75 J
- (d)
1.25 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°
How long will it take to perform 440 J of work at the rate of 11 W?
- (a)
50 s
- (b)
40 s
- (c)
30 s
- (d)
20 s
A man with a box on his head is climbing up a ladder. What work is said to be done by the man on the box
- (a)
Positive
- (b)
Negative
- (c)
Zero
- (d)
Undefined
A ball is thrown upwards from point A. It reaches up to point 8 and returns. What can be concluded?
- (a)
Kinetic energy at A = kinetic energy at B
- (b)
Potential energy at A = potential energy at B
- (c)
Potential energy at B = kinetic energy at B
- (d)
Potential energy at B = kinetic energy at A
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
800 g ball is pulled up a slope as shown in the figure.
Calculate the potential energy it gains.
- (a)
1.96 J
- (b)
1.57 J
- (c)
7.84 J
- (d)
1.26 J
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 lorry and a car with the same kinetic energy are brought to rest by the application of brakes which provide equal retarding forces. Which of them will come to rest in a shorter distance?
- (a)
Lorry
- (b)
Car
- (c)
Both will stop at the same distance
- (d)
Car stops first but takes longer distance
What should be the angle between the force and displacement for maximum work?
- (a)
0°
- (b)
30°
- (c)
60°
- (d)
90°
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)
The rectangular components of a force are applied to move a body. One of the components is 30 N.What should be the other component to obtain a resultant force of 50 N
- (a)
30 N
- (b)
40 N
- (c)
50 N
- (d)
90 N
Water is falling at the rate of 1000 kg per second. The height of the fall is about 100m.The potential energy of water when it falls on the blades will be conveyed to them and P.E.is converted into K.E. of blades. Estimate the power that could be generated, if energy is not lost otherwise (Take the value of 'g' as 10ms-2).
- (a)
lOW
- (b)
100 W
- (c)
106W
- (d)
105W
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
A girl of mass 40 kg climbs 50 stairs each of average height 20 cm in 50 s.Find the power of the girl (g = 10ms-2).
- (a)
50 W
- (b)
50 x 20 W
- (c)
80 W
- (d)
50 x 20 x2W
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
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
An engine of 4.9 kW power is used to pump water from a well which is 20 m deep. What quantity of water in kilolitres can it pump out in 30 minutes?
- (a)
45k/
- (b)
75k/
- (c)
25 k/
- (d)
90 k/
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
Three different stones P,Q and R of different weights are lifted from the ground level to different heights on different planets as given below:
Which of the following statements is true? (Given that the acceleration due to gravity on the Earth, the Saturn and the Jupiter are 10m S-2, 15 m S-2 and 25 m S-2 respectively).
- (a)
More energy is required to lift stone Q than stone P.
- (b)
More energy is required to lift stone P than stone R.
- (c)
Stone P and stone Q require the same amount of energy.
- (d)
Stone Pand stone Rrequire the same amount of energy.
A ball is projected upwards. As it rises, there is an increase in its
- (a)
momentum
- (b)
retardation
- (c)
kinetic energy
- (d)
potential energy
A ball of mass 2 kg and another of mass 4 kg are dropped together from a 60 feet tall building. What will be the ratio of their kinetic energies after a fall of 30 feet?
- (a)
\(\sqrt { 2 } \):1
- (b)
1: 4
- (c)
1: 2
- (d)
1: \(\sqrt { 2 } \)
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.
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.