Practicing Class 9 Science MCQ and Class 9 Science Exploration Chapter 7 MCQ Online Test with Answers Work Energy and Simple Machines daily helps in time management.
Class 9 Science Chapter 7 Work Energy and Simple Machines MCQ
Work Energy and Simple Machines MCQ
Class 9 Science Chapter 7 MCQ online test
Question 1.
Work is done when a force acting on an object:
(a) causes no displacement
(b) acts perpendicular to the direction of motion
(c) causes displacement in its direction
(d) is not applied at all
Answer:
(c) causes displacement in its direction
Question 2.
The SI unit of work is:
(a) Watt
(b) Joule
(c) Newton
(d) Pascal
Answer:
(b) Joule
Question 3.
If the velocity of a body is doubled, its kinetic energy:
(a) becomes 4 times
(b) becomes 2 times
(c) becomes times
(d) remains the same
Answer:
(a) becomes 4 times
Question 4.
A 1 kg stone is raised to a height of 10 m (g = 10 m/s2). The potential energy gained is:
(a) 100 J
(b) 10 J
(c) 1000 J
(d) 1 J
Answer:
(a) 100 J
Question 5.
When a body falls freely towards the Earth, its total energy:
(a) increases
(b) decreases
(c) remains constant
(d) first increases, then decreases
Answer:
(c) remains constant
Question 6.
A coolie was standing with 2 suitcases on his head and 2 bags in his hand. The luggage exerted a force of 159 N on him. What is the amount of work done by him?
(a) 79.5 J
(b) 318 J
(c) 0 J
(d) 159 J
Answer:
(c) 0 J
Question 7.
What is the work done by a girl carrying a 5 kg bag from the ground floor to the first floor (2 m high)?
(a) 100 J
(b) 10 J
(c) 50 J
(d) 25 J
Answer:
(a) 100 J
Question 8.
Calculate the distance between the man and the box when the work done to move the box was 100 J with a force of 15 N.
(a) 6 m
(b) 16.6m
(c) 26.6 m
(d) 6.6 m
Answer:
(d) 6.6 m
Question 9.
What is the fixed point upon which a lever rotates?
(a) Effort
(b) Load
(c) Fulcrum
(d) Axis
Answer:
(c) Fulcrum
Question 10.
A pulley system is an example of a machine that:
(a) Reduces the work required
(b) Changes the direction of force
(c) Always has 100% efficiency
(d) Decreases energy
Answer:
(b) Changes the direction of force
Question 11.
A 1 kg mass has a kinetic energy of 1 joule when its speed is
(a) 0.45 m/s
(b) 1 m/s
(c) 1.4 m/s
(d) 4.4 m/s
Answer:
(c) 1.4 m/s
Question 12.
Two particles of masses 1 g and 4 g have equal kinetic energies. What is the ratio between their momenta?
(a) 1 : 4
(b) 1 : 8
(c) 1 : 2
(d) 1 : 16
Answer:
(c) 1 : 2
Question 13.
If the speed of a motor car increases by six times, its kinetic energy will increase by
(a) 6 times
(b) 12 times
(c) 24 times
(d) 36 times
Answer:
(d) 36 times
Question 14.
Two bodies of equal weight are kept at heights of h and 1.5 h, respectively. The ratio of their PE is
(a) 3 : 2
(b) 2 : 3
(c) 1 : 1
(d) 4 : 3
Answer:
(b) 2 : 3
Question 15.
The acceleration due to gravity on the moon is one-sixth that on earth. A high-jumper can jump 2 m on earth. What height can he jump on the moon?
(a) 2 m
(b) 6 m
(c) 8 m
(d) 12 m
Answer:
(d) 12 m
Question 16.
If a stone of mass m falls a vertical distance d, the decrease in gravitational potential energy is
(a) mg/d
(b) md2/2
(c) mgd
(d) md/g
Answer:
(c) mgd
Question 17.
A body is falling from a height h. After it has fallen a height hi2, it will possess: (NCERT Exemplar)
(a) only potential energy
(b) only kinetic energy
(c) half potential and half kinetic energy
(d) more kinetic and less potential energy
Answer:
(c) half potential and half kinetic energy
Question 18.
When a body falls freely towards the earth, then its total energy (NCERT Exemplar)
(a) increases
(b) decreases
(c) remains constant
(d) first increases and then decreases
Answer:
(c) remains constant
Question 19.
Potential energy of your body is minimum when you
(a) are standing
(b) are sitting on a chair
(c) are sitting on the ground
(d) lie down on the ground
Answer:
(d) lie down on the ground
Question 20.
An iron sphere of mass 10 kg has the same diameter as an aluminium sphere of mass is 3.5 kg. Both spheres are dropped simultaneously from tower. When they are 10 m above the ground, they have the same (NCERT Exemplar)
(a) acceleration
(b) momenta
(c) potential energy
(d) kinetic energy
Answer:
(a) acceleration
Question 21.
When a body falls freely towards the earths then, its total energy:
(a) increases
(b) decreases
(c) remains constant
(d) first increases and then decreases
Answer:
(c) When a body falls freely towards the earth, its potential energy decreases, which in turn increases the kinetic energy. Therefore, its total energy remains constant.
Question 22.
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
Answer:
(a) In the given process, the potential energy of the car does not change as it does not depend on velocity.
Question 23.
In case of negative work, the angle between the force and displacement is:
(a) 0°
(b) 45°
(c) 90°
(d) 180°
Answer:
(d) Work done is negative when force acts opposite to the direction of displacement, i.e. the angle between the two directions is 180.
Question 24.
An iron sphere of mass 10 kg has the same diameter as an aluminium sphere of mass is 3.5 kg. Both spheres are dropped simultaneously from a tower. When they are 10 m above the ground, they have the same:
(a) acceleration
(b) momenta
(c) potential energy
(d) kinetic energy
Answer:
(a) Both spheres have the same acceleration that is acceleration due to gravity, g. Momentum, potential energy, and kinetic energy depend on mass, which is different for the two spheres, and hence the quantities will differ for the two spheres.
Question 25.
A girl is carrying a school bag of 3 kg mass on her back and moves 200 m on a levelled road. The work done against the gravitational force will be (g =10 ms-2)
(a) 6 × 103J
(b) 6 J
(c) 0.6 J
(d) zero
Answer:
(d) The gravitational force on the bag, i.e., the weight of bag, is in vertically downward direction, whereas the distance moved by her is in horizontal direction. It means that the force and displacement are perpendicular to each other; therefore, no work is done.
Question 26.
Which one of the following is not the unit of energy?
(a) joule
(b) newton metre
(c) kilowatt
(d) kilowatt hour
Answer:
(c) Kilowatt is the unit of power, not of energy.
Question 27.
The work done on an object does not depend upon the
(a) displacement
(b) force applied
(c) angle between force and displacement
(d) initial velocity of the object
Answer:
(d) The work done on an object does not depend upon the initial velocity of the object.
Question 28.
Water stored in a dam possesses
(a) no energy
(b) electrical energy
(c) kinetic energy
(d) potential energy
Answer:
(d) Water stored in a dam possesses potential energy as it is stored at a certain height from the ground level.
Question 29.
A body is falling from a height h/2. After it has fallen a height h/2, it will possess
(a) only potential energy
(b) only kinetic energy
(c) half potential and half kinetic energy
(d) more kinetic and less potential energy
Answer:
(c) When a body falls from a height h/2, its potential energy becomes half (as potential energy = mgh). The rest half of initial potential energy gets converted into kinetic energy. Hence, the body will possess half potential energy and half kinetic energy.
Work Energy and Simple Machines Class 9 Assertion and Reason Questions
Directions: For Questions number (1) to (3), two statements are given – one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
(a) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
(b) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).
(c) Assertion (A) is true, but Reason (R) is false.
(d) Assertion (A) is false, but Reason (R) is true.
Question 1.
Assertion (A): The work done by gravitational force on an object moving along a horizontal path is zero.
Reason (R): The direction of force (gravity) is perpendicular to the direction of displacement.
Answer:
(a) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
Question 2.
Assertion (A): The kinetic energy of a body increases if its mass is doubled while keeping velocity constant.
Reason (R): Kinetic energy is inversely proportional to the mass of the object.
Answer:
(c) Assertion (A) is true, but Reason (R) is false.
Question 3.
Assertion (A): A person holding a heavy suitcase standing at a bus stop does no work in the sense of physics.
Reason (R): Force is being applied, but there is no displacement.
Answer:
(a) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
Work Energy and Simple Machines Class 9 Fill in the Blanks
1. The SI unit of work and energy is __________.
Answer:
Joule (J)
2. The capacity to do work is known as __________.
Answer:
Energy
3. The energy possessed by a body due to its position or configuration is called __________.
Answer:
Potential energy (P.E.)
4. A __________ consists of a wheel and a rope, used to lift heavy loads.
Answer:
Pulley
5. A __________ is a rigid bar that rotates around a fixed point, such as a scissor.
Answer:
Lever
Work Energy and Simple Machines Class 9 True or False
1. Work is done when you push against a wall even if it doesn’t move.
Answer:
False
2. The SI unit of work and energy is the same (Joule).
Answer:
True
3. Kinetic energy of an object doubles if its velocity is doubled.
Answer:
False
4. Energy can neither be created nor destroyed.
Answer:
True
5. Power is the rate of doing work.
Answer:
True
MCQ On Work Energy and Simple Machines Class 9 for Practice
Choose the correct option in the following questions
Question 1.
Work done is measured by
(a) mass × velocity
(b) mass × acceleration
(c) force × distance
(d) force × time
Question 2.
A body is under the action of the equal and opposite forces, each of 5 N. The body is displaced by 2 m. The work done is
(a) + 10 J
(b) – 10 J
(c) zero
(d) 25 J
Question 3.
The work done on a body does not depend upon the
(a) force applied
(b) displacement
(c) initial velocity of the body
(d) angle at which force is inclined to the displacement
Question 4.
A load is carried through a distance of5m in the following different ways. In which case the work done is (i) maximum and (ii) minimum?
(a) Pushed over an inclined plane
(b) Liften vertically upward
(c) Pushed over smooth rollers
(d) Pushed on a plane horizontal surface
Question 5.
Which one of the following is not the unit of energy?
(a) joule
(b) newton metre
(c) kilowatt
(d) kilowatt hour
Question 6.
Newton-metre is the unit of
(a) power
(b) work
(c) momentum
(d) gravitational intensity
Question 7.
A body is acted upon by a force which is proportional to the distance covered. If distance covered be denoted by S, then work done by the force will be proportional to
(a) S
(b) S2
(c) S3/2
(d) S2/3
Question 8.
A body starts from rest and acquires a velocity v in time T. The work done on the body in time t will be proportional to
(a) \(\frac{V}{T}\)t
(b) \(\frac{V^2}{T}\) t
(c) \(\frac{V^2}{T^2}\) t
(d) \(\frac{V^2}{T^2}\) t2
Question 9.
A man of mass 50 kg walks up to the top of a building of height 20 m above the ground level. The increase in his P.E. is
(a) 2450J
(b) 9800J
(c) 10,000 J
(d) 3648 J
Question 10.
Water stored in a dam possesses
(a) no energy
(b) electrical energy
(c) kinetic energy
(d) potential energy
Question 11.
When the speed of a moving object is doubled, its
(a) acceleration is doubled
(b) weight is doubled
(c) kinetic energy is doubled
(d) kinetic energy increases four times
Question 12.
The kinetic energy of a body decreases by 10 %. What is the percentage decrease in momentum?
(a) 10
(b) 20
(c) 30
(d) None of these
Assertion-Reason Questions
Directions: For Questions number (1) to (3), two statements are given — one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
(a) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
(b) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).
(c) Assertion (A) is true, but Reason (R) is false.
(d) Assertion (A) is false, but Reason (R) is true.
Question 1.
Assertion (A): Kinetic energy of a body is quadrupled, when its velocity is doubled.
Reason (R): Kinetic energy is proportional to the square of velocity.
Question 2.
Assertion (A): According to the law of conservation of mechanical energy, the change in potential energy is equal and opposite to the change in kinetic energy.
Reason (R): Mechanical energy is not a conserved quantity.
Question 3.
Assertion (A): A light body and a heavy body have same momentum. They also have same kinetic energy.
Reason (R): Kinetic energy does not depend on mass of the body.
Fill in the Blanks
1. The SI unit of energy is __________.
2. Mechanical advantage = __________.
3. The kinetic energy of a body is by virtue of its __________.
4. Work is said to be done if a force __________ a body through a certain distance in the direction of force.
5. The rate of doing work is called __________.
State whether the statements given below are True or False
1. A simple machine makes our work very hard.
2. An inclined plane is used to move objects to a higher level.
3. A lever consists of fulcrum, load and effort.
4. A stapler is an example of fixed pulley.
5. A pulley is a simple machine used to lift heavy loads.
Match the Columns
Question 1.
| Column A (Concept/Term) | Column B (Definition/Unit/Formula) |
| 1. Work Done | (a) Energy stored due to position or height (mgh) |
| 2. Energy | (b) Energy possessed by an object due to its motion (1/2 mv2) |
| 3. Kinetic Energy | (c) The capacity or ability to do work |
| 4. Potential Energy | (d) Product of Force and Displacement w = f × s) |
Question 2.
| Column A (Concept/Term) | Column B (Definition/Unit/Formula) |
| 1. Power | (a) A device that makes work easier by changing force or direction |
| 2. Simple Machine | (b) SI unit of Power |
| 3. Joule (J) | (c) SI unit of both Work and Energy |
| 4. Watt (W) | (d) Rate of doing work (p = w/t) |