CBSE Questions for Class 9 Physics Work And Energy Quiz 12 - MCQExams.com

A particle is acted upon by a force F which varies with position x as shown in the figure. If the particle at $$x=0$$ has the kinetic energy of $$25$$ J, then the kinetic energy of the particle at $$x=16$$m is?
1208470_a40f7e31514246c2ad656b86645125c1.png
  • $$45$$J
  • $$30$$J
  • $$70$$J
  • $$135$$J
An object of mass $$5 \ kg$$  falls from rest through a vertical distance of $$20 \ m$$ and reaches a velocity of $$10 \ m/s$$. How much work is done by the push of the air on the object?
  • $$-740 \ J$$ 
  • $$-750 \ J$$ 
  • $$-760 \ J$$ 
  • $$-770 \ J$$ 
An elevator is run by the cables at constant speed. The total work done by the elevator is:
  • Negative
  • Positive
  • Zero
  • Positive or negative depending on the direction of motion
Kinetic energy of the liquid per unit mass is
  • $$\frac { 1 } { 2 } m v ^ { 2 }$$
  • $$\frac { 1 } { 2 } v ^ { 2 }$$
  • $$\frac { 1 } { 2 } m ^ { 2 } v$$
  • $$m v ^ { 2 }$$
When the mass of body is halved and velocity is doubled, then the kinetic energy of the body 
  • remains same
  • is doubled
  • is 4 times
  • is $$\frac{1}{4}$$ th
Mass of $$B$$ is four times that of $$A . B$$ moves with a velocity half that of $$A$$. Then, $$B$$ has 
  • kinetic energy equal to that of $$A$$
  • half the kinetic energy of $$A$$
  • twice the kinetic energy of $$A$$
  • kinetic energy one-fourth of $$A$$
A body of mass $$15\ kg$$ moving with a velocity of $$10\ ms^{-1}$$ is bought to rest. The work done by the brake is
  • $$-250\ J$$
  • $$-500\ J$$
  • $$-750\ J$$
  • $$-1000\ J$$
If the unit of force and length each be increased by four times, then the unit of energy is increased by
  • $$16$$ times
  • $$8$$ times
  • $$2$$ times
  • $$4$$ times
 Work is always done on a body when
  • a force acts on body to displace it.
  • it moves through a certain distance.
  • it experiences an increase in energy through a mechanical influence.
  • there is no displacement.
The amount of work done on an object when a constant force of $$\dfrac { 1 }{ 10 }\ N$$ displaces it by $$10\ cm$$ along the line of action of the force is:
  • $$\dfrac { 1 }{ 10 }\ J$$
  • $$\dfrac { 1 }{ 100 }\ J$$
  • $$1\ J$$
  • $$10\ J$$
A lawn roller is pulled along a horizontal surface through a distance of $$20 \ m$$ by a rope with a force of $$200 \ N$$. If the rope makes an angle of $$60^o$$ with the vertical while pulling, the amount of work done by the pulling force is:
  • $$3464 \mathrm { J }$$
  • $$1000 \mathrm { J }$$
  • $$2000 \sqrt { 3 } \mathrm { J }$$
  • $$2000 \mathrm { J }$$
The SI unit of work is newton.
  • True
  • False
In $$10 s$$, a body of $$6 kg$$ mass is dragged $$8 m$$ with uniform velocity across a floor by a steady force of $$20 N$$. The K.E of the body is:
  • $$2.92 J$$
  • $$0.92 J$$
  • $$1.92 J$$
  • $$0J$$
The $$SI$$ unit of energy, the Joule is equivalent to 
  • $$N-m$$
  • $$W/s$$
  • $$N-m^{2}/s^{2}$$
  • $$N/m$$
A body of mass m is rotating in a vertical circle of radius 'r' with critical speed. The difference in its K.E. at the top and the bottom is _____.
  • 2mgr
  • 4 mgr
  • 6 mgr
  • 3 mgr
A body of mass 0.5 kg is moving at a constant velocity, work done is
  • 0 J
  • 1.0 J
  • 2.0 J
  • 4.0 J
In which of the following, law of conservation of energy is violated? 
  • Fusion of nuclei
  • Mud thrown on a wall
  • A satellite moving in elliptical orbit
  • None of these
If the kinetic Energy possessed by a man of $$50$$kg is $$625J$$, the speed of man is 
  • $$5m{s^{ - 1}}$$
  • $$50m{s^{ - 1}}$$
  • $$0.5m{s^{ - 1}}$$
  • $$500m{s^{ - 1}}$$
A man of mass 20 kg is running in a straight line with velocity 10 m/s. What is value of his kinetic energy?
  • $$10\ J$$
  • $$100\ J$$
  • $$1000\ J$$
  • $$10000\ J$$
The power exerted on the body at $$2\ s$$ is:
  • $$50\ W$$
  • $$100\ W$$
  • $$150\ W$$
  • $$200\ W$$
Two men $$A$$ and $$B$$ each weighing $$80\ kg$$, run up the same stair case. While $$A$$ does it in $$20\ s, B$$ does it in $$15\ s$$. The ratio of the powers developed by $$A$$ and $$B$$ is
  • $$\dfrac{4}{3}$$
  • $$\dfrac{3}{4}$$
  • $$\dfrac{1}{2}$$
  • $$\dfrac{1}{4}$$
Two bodies traveling with velocity $$20ms^{-1}$$ and $$40ms^{-1}$$ have same K.E. If the mass of the body having velocity $$40ms^{-1}$$ is 8 kg the mass of other body is 
  • 8 Kg
  • 16 kg
  • 24 kg
  • 32 kg
Which of the following does not possess the ability to do work because of motion?
  • A sparrow flying in the sky
  • A sparrow moving slowly on the ground
  • A sparrow in the nest on a tree
  • A squirrel going up a tree
How much height must an object of mass $$5kg$$ be lifted to have potential energy $$5000J$$ ?$$[g=10 m/s^2]$$
  • $$100m$$
  • $$50m$$
  • $$120m$$
  • $$110m$$
A car is accelerated on a levelled road and attains a speed of $$5$$ times its initial speed. In this process , the kinetic energy of the car:
  • does not change
  • becomes $$4$$ times that of initial kinetic energy
  • becomes $$8$$ times that of initial kinetic energy
  • becomes $$25$$ times that of initial kinetic energy
No work is done when:
  • a nail is hammered into a wooden box
  • a box is pushed along horizontal floor
  • there is no component of force, parallel to the direction of motion
  • none of these
Potential energy of a person is minimum when:
  • Person is standing
  • Person is sitting on a chair
  • Person is sitting on the ground
  • Person is lying on the ground
A stone is thrown upwards as shown in the diagram. When it reaches $$P,$$ which of the following has the greatest value for the stone?
1764149_46e1a30f3d4647b3b5ac1ddd2ab130c8.png
  • its acceleration
  • its kinetic energy
  • its potential energy
  • its weight
Write true or false for the following statements:
If we know the speed and mass of an object, we can find out its kinetic energy.
  • True
  • False
The SI unit of work is Watt.
  • True
  • False
0:0:1


Answered Not Answered Not Visited Correct : 0 Incorrect : 0

Practice Class 9 Physics Quiz Questions and Answers