CBSE Class 9 Science Chapter 07 Work, Energy, And Simple Machines MCQs Set 03

Practice MCQs for Class 9 Science Chapter 07 Work, Energy, And Simple Machines

Review structured MCQ sets for Class 9 Science Chapter 07 Work, Energy, And Simple Machines. Built according to official CBSE guidelines, these downloadable questions support daily revision and core concept reinforcement.

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Access the complete set of multiple-choice questions for Chapter 07 Work, Energy, And Simple Machines below. This focused format allows students to isolate specific topics for thorough review and uninterrupted practice alongside official CBSE textbooks.

Question: A force is applied to an object, causing it to move 5 metres in the direction of the force. If the same force were applied but the object moved only 2.5 metres in the same direction, how would the work done in the second case compare to the first?
A. It would be twice as much
B. It would be half as much
C. It would be the same
D. It would be one-quarter as much
Show Answer & Explanation

Answer: (B) It would be half as much

Explanation:
Work is calculated as force multiplied by displacement in the direction of force. If displacement is reduced to half, and force remains constant, the work done is also halved.

Question: A stretched spring is held in its deformed state and then suddenly released, propelling a block forward. Which of the following correctly describes the sequence of energy transformations?
A. Kinetic energy is converted to elastic potential energy
B. Elastic potential energy is converted to kinetic energy
C. Elastic potential energy is converted to gravitational potential energy
D. Thermal energy is converted to kinetic energy
Show Answer & Explanation

Answer: (B) Elastic potential energy is converted to kinetic energy

Explanation:
The deformed spring stores elastic potential energy in its configuration. Upon release, this stored energy is converted into the kinetic energy of the moving block.

Question: A box is pushed horizontally with constant force F across a rough floor, and it moves a distance d in the direction of the push. Later, the same box is pushed with force 2F over the same distance d. What is the ratio of work done in the second scenario to the first scenario?
A. 1:1
B. 1:2
C. 2:1
D. 4:1
Show Answer & Explanation

Answer: (C) 2:1

Explanation:
Work depends on both force and displacement. When force doubles while displacement remains the same, work also doubles. The ratio is therefore 2:1.

Question: A motorcycle accelerates from rest on a horizontal road. The engine does work on the motorcycle, increasing its speed. According to the work-energy theorem, what must be happening to the motorcycle's kinetic energy?
A. It remains zero
B. It is decreasing
C. It is increasing
D. It stays constant
Show Answer & Explanation

Answer: (C) It is increasing

Explanation:
The work-energy theorem states that work done on an object equals its change in energy. Since the engine does positive work, the motorcycle gains kinetic energy as its speed increases.

Question: A ball is released from rest at the top of a smooth, frictionless inclined plane. As the ball slides down, gravitational potential energy is converted to kinetic energy. At the bottom of the incline, which statement accurately reflects the ball's total mechanical energy compared to the top?
A. Mechanical energy increases
B. Mechanical energy decreases
C. Mechanical energy remains the same
D. Mechanical energy becomes zero
Show Answer & Explanation

Answer: (C) Mechanical energy remains the same

Explanation:
In the absence of friction and other dissipative forces, mechanical energy is conserved. The loss in potential energy as the ball descends equals the gain in kinetic energy, keeping total mechanical energy constant.

Question: A person rides a bicycle up a hill at a constant, slow pace. Another cyclist covers the same vertical distance in half the time. Assuming both cyclists have similar mass and climb to the same height, how do their power outputs compare?
A. Both have the same power output
B. The faster cyclist has twice the power output
C. The slower cyclist has twice the power output
D. Cannot be determined without knowing their masses
Show Answer & Explanation

Answer: (B) The faster cyclist has twice the power output

Explanation:
• Both cyclists do the same amount of work (same mass × same height).
• Power = work / time.
• The faster cyclist completes the work in half the time.
• Therefore, power output is inversely proportional to time; faster completion means higher power.

Question: A moving cricket ball collides with and knocks over stationary wickets. Which form of energy is primarily responsible for the wickets' motion after the collision?
A. Potential energy of the ball
B. Thermal energy of the wickets
C. Kinetic energy transferred from the ball
D. Chemical energy stored in the wickets
Show Answer & Explanation

Answer: (C) Kinetic energy transferred from the ball

Explanation:
The moving ball possesses kinetic energy due to its motion. Upon collision, some of this kinetic energy is transferred to the wickets, giving them the energy needed to move and fall.

Question: According to the work-energy theorem, if a constant force acts on a stationary object and the object accelerates in the direction of the force, what must be true about the work done and the object's kinetic energy?
A. Work done is zero, kinetic energy is zero
B. Work done is positive, kinetic energy increases
C. Work done is negative, kinetic energy decreases
D. Work done equals zero, kinetic energy remains unchanged
Show Answer & Explanation

Answer: (B) Work done is positive, kinetic energy increases

Explanation:
When positive work is done on an object, it gains energy in the form of increased kinetic energy. The work done equals the change in kinetic energy.

Question: A student carefully measures the force needed to pull a cart up a smooth inclined plane and compares it to the force required to lift the cart vertically to the same height. Why does the inclined plane require less force?
A. The distance along the incline is longer than the vertical height
B. The mass of the cart decreases on an incline
C. Gravity acts differently on an incline
D. The angle of the incline eliminates friction entirely
Show Answer & Explanation

Answer: (A) The distance along the incline is longer than the vertical height

Explanation:
Work done equals force times displacement. On an incline, although the force is smaller, the displacement along the slope is larger than the vertical height, keeping total work constant. Simple machines reduce force by increasing the distance over which it acts.

Question: A lever is used to lift a heavy load. The effort arm is 4 metres long and the load arm is 1 metre long. What is the mechanical advantage of this lever?
A. 0.25
B. 1
C. 4
D. 5
Show Answer & Explanation

Answer: (C) 4

Explanation:
Mechanical advantage of a lever equals the ratio of effort arm to load arm. Here, 4 m ÷ 1 m = 4. This means the lever allows the application of one-quarter the force normally needed to lift the load.

Question: A ball of mass m is thrown straight up with initial velocity v₀. At the highest point of its flight, the ball momentarily has zero velocity. Which statement about the ball's energy is most accurate at this highest point?
A. Both kinetic and potential energy are zero
B. Kinetic energy is maximum, potential energy is zero
C. Kinetic energy is zero, potential energy is maximum
D. Both kinetic and potential energy are equal
Show Answer & Explanation

Answer: (C) Kinetic energy is zero, potential energy is maximum

Explanation:
At the highest point, all the initial kinetic energy has been converted to gravitational potential energy, so kinetic energy becomes zero while potential energy reaches its maximum value.

Question: In a simple pulley system, a fixed pulley is used to raise a flag by pulling a rope downward. The tension in the rope equals the weight of the flag. What does this tell us about the mechanical advantage?
A. The mechanical advantage is greater than 1
B. The mechanical advantage is exactly 1
C. The mechanical advantage is less than 1
D. The mechanical advantage cannot be determined
Show Answer & Explanation

Answer: (B) The mechanical advantage is exactly 1

Explanation:
A fixed pulley changes the direction of the applied force but does not reduce the magnitude of force required. Since the effort equals the load, the mechanical advantage is 1.

Question: A stretched rubber band is held in place and contains stored energy due to its deformation. This stored energy is most accurately described as which type of energy?
A. Kinetic energy
B. Elastic potential energy
C. Gravitational potential energy
D. Thermal energy
Show Answer & Explanation

Answer: (B) Elastic potential energy

Explanation:
Elastic potential energy is the energy stored in an object due to its deformation or stretching. A stretched rubber band possesses this form of energy in its deformed state.

Question: Two identical objects are raised to the same height above the ground—one on Earth and one on the Moon, where gravitational acceleration is one-sixth that of Earth. How do their gravitational potential energies compare?
A. The object on Earth has six times more potential energy
B. The object on the Moon has six times more potential energy
C. Both have equal potential energy
D. The comparison cannot be made without knowing the masses
Show Answer & Explanation

Answer: (A) The object on Earth has six times more potential energy

Explanation:
Potential energy is calculated as U = mgh. Since g on the Moon is one-sixth that of Earth, and the mass and height are the same, the object on Earth has six times greater potential energy.

Question: A conservation expert uses a seesaw-like lever to pry open a stuck wooden door. The fulcrum is positioned closer to the door than to where the effort is applied. Based on lever mechanics, how does the mechanical advantage compare to a lever where the fulcrum is at the midpoint?
A. The mechanical advantage is smaller
B. The mechanical advantage is larger
C. The mechanical advantage is the same
D. It cannot be determined without measurements
Show Answer & Explanation

Answer: (B) The mechanical advantage is larger

Explanation:
• Mechanical advantage of a lever = effort arm / load arm.
• When the fulcrum is closer to the door (load), the load arm decreases.
• A smaller load arm means a larger mechanical advantage.
• Therefore, this arrangement provides greater mechanical advantage than a centered fulcrum.

Question: A student slowly raises a heavy box vertically using her hands, holding it briefly at a certain height, and then slowly lowers it back to the ground. During which of these three phases does the student do negative work on the box?
A. During the upward lifting phase
B. While holding it steady at height
C. During the downward lowering phase
D. During both lifting and holding phases
Show Answer & Explanation

Answer: (C) During the downward lowering phase

Explanation:
Negative work occurs when force and displacement are in opposite directions. As the student lowers the box, her hand applies an upward force to control the descent, but the box moves downward, making force and displacement opposite. During lifting, both force and displacement point upward (positive work). While holding steady, there is no displacement, so no work is done.

Question: In a certain collision, a moving ball transfers some of its kinetic energy to a stationary object, causing the object to move. According to the work-energy theorem, what does the work done by the ball on the stationary object equal?
A. The initial kinetic energy of the ball
B. The change in kinetic energy of the stationary object
C. The loss in kinetic energy of the moving ball
D. The potential energy gained by the stationary object
Show Answer & Explanation

Answer: (B) The change in kinetic energy of the stationary object

Explanation:
The work-energy theorem states that work done on an object equals the change in its energy. The stationary object begins with zero kinetic energy and gains kinetic energy as it moves after being struck. The work done by the ball on this object therefore equals the object's change in kinetic energy (final minus initial).

Question: A child slides down a frictionless slide starting from rest at height h. At the bottom, the child has velocity v such that v² = 2gh. If a second child of different mass starts from the same height on the same frictionless slide, which statement correctly predicts that child's velocity at the bottom?
A. The velocity will be smaller because the second child has greater mass
B. The velocity will be the same because it depends only on height, not mass
C. The velocity will be larger if the second child is heavier
D. The velocity will be different but predictable only if we know the second child's exact mass
Show Answer & Explanation

Answer: (B) The velocity will be the same because it depends only on height, not mass

Explanation:
From the conservation of mechanical energy, mgh (potential energy at top) converts entirely to ½mv² (kinetic energy at bottom) when friction is absent. Solving gives v = √(2gh), which contains no mass term. The velocity at the bottom depends only on the height fallen and gravitational acceleration, not on the object's mass, making this a key result of energy conservation.

Question: A force-displacement graph shows that a constant 10 N force is applied to an object over a displacement of 1 metre in the direction of the force. If you were to calculate the work done using this graph, which geometric feature of the graph would give you the answer?
A. The slope of the line
B. The area under the curve
C. The y-intercept value
D. The distance from the origin to the endpoint
Show Answer & Explanation

Answer: (B) The area under the curve

Explanation:
Work done equals force multiplied by displacement in the direction of the force. On a force-displacement graph, this product corresponds to the area under the curve. For a constant force, this area is a rectangle with height equal to the force and width equal to displacement, yielding 10 N × 1 m = 10 J.

Question: A person uses a fixed pulley to raise a flag by pulling a rope downward with a force of 50 N. The flag weighs 50 N. What is the mechanical advantage of this fixed pulley system, and what does this value tell us about the pulley's primary function?
A. MA = 2; it reduces the force needed
B. MA = 1; it only changes the direction of the applied force
C. MA = 0.5; it requires more effort than lifting directly
D. MA = 50; it is designed for very heavy loads
Show Answer & Explanation

Answer: (B) MA = 1; it only changes the direction of the applied force

Explanation:
• Mechanical advantage = load ÷ effort = 50 N ÷ 50 N = 1
• Fixed pulleys have MA = 1 because the effort force must equal the load
• The pulley's benefit is directional—it is easier to pull downward than to lift upward, but no force reduction occurs
• The pulley provides convenience, not mechanical efficiency in terms of reduced effort

Question: A moving cricket ball strikes stationary wickets and transfers energy to them, causing the wickets to fall over. Which form of energy that the ball possessed before the collision is primarily responsible for the wickets' subsequent motion?
A. Potential energy stored in Earth's gravitational field
B. Kinetic energy due to the ball's motion
C. Elastic potential energy stored within the ball's material
D. Thermal energy from friction with the air
Show Answer & Explanation

Answer: (B) Kinetic energy due to the ball's motion

Explanation:
The moving ball possesses kinetic energy due to its velocity. When the ball collides with the stationary wickets, this kinetic energy is transferred through the collision, doing work on the wickets and causing them to accelerate and topple. Potential energy is stored energy related to position, not motion, making kinetic energy the appropriate answer here.

Question: An archer pulls back a bow string, bending the bow's arms in the process. Just before releasing the arrow, where is the energy that will propel the arrow stored, and what type of energy is it?
A. In the arrow's motion; kinetic energy
B. In the bent bow's shape; elastic potential energy
C. In the Earth's gravitational field; gravitational potential energy
D. In the friction between the bow and string; thermal energy
Show Answer & Explanation

Answer: (B) In the bent bow's shape; elastic potential energy

Explanation:
When the bow's arms are bent, work is done against the internal forces holding the bow's shape. This work is stored as elastic potential energy in the deformed material. When released, the internal forces undo the deformation, and this stored elastic potential energy converts to the arrow's kinetic energy.

Question: Two workers carry identical boxes up the same ramp to a platform. Worker A completes the task in 2 minutes while Worker B completes it in 4 minutes. Assuming both workers exert approximately the same total effort in moving the box to the same height, which statement correctly compares their power outputs?
A. Worker A and B have equal power because they do the same total work
B. Worker A has twice the power output because he completes the task in half the time
C. Worker B has greater power because he takes longer and must apply more force
D. Their power outputs cannot be compared without knowing the mass of the box
Show Answer & Explanation

Answer: (B) Worker A has twice the power output because he completes the task in half the time

Explanation:
Power is defined as work done divided by time taken. Both workers do the same work (moving the same box to the same height), but Worker A does this work in half the time. Since P = W/t, halving the time doubles the power output. Worker A's power is therefore twice that of Worker B.

Question: A seesaw is balanced with a 40 kg child sitting 3 metres from the fulcrum on one side and an 80 kg adult sitting at some distance on the opposite side. Using the lever principle, at what distance from the fulcrum must the adult sit to maintain balance?
A. 1.5 metres
B. 2 metres
C. 3 metres
D. 6 metres
Show Answer & Explanation

Answer: (A) 1.5 metres

Explanation:
A lever balances when effort × effort arm = load × load arm, or equivalently, mass₁ × distance₁ = mass₂ × distance₂. Here, 40 kg × 3 m = 80 kg × distance, giving distance = (40 × 3) ÷ 80 = 120 ÷ 80 = 1.5 m. The heavier adult must sit closer to the fulcrum to achieve balance.

Question: A crane lifts a mass to the 10th floor of a building in a time t, then lifts the same mass to the 20th floor (which is twice the height) in a time 2t. How do the power requirements for these two lifts compare, and why?
A. The power for the second lift is half that of the first because it takes twice as long
B. The power for both lifts is equal because the mass is identical
C. The power for the second lift equals the power for the first because doubling both work and time keeps power constant
D. The power for the second lift is twice that of the first because twice the work must be done
Show Answer & Explanation

Answer: (C) The power for the second lift equals the power for the first because doubling both work and time keeps power constant

Explanation:
Work done in the first lift is mgh (where h is the height per floor). In the second lift, work is mg(2h) = 2mgh. Time increases from t to 2t. Power₁ = mgh/t and Power₂ = 2mgh/(2t) = mgh/t. The powers are equal because the doubling of work is offset by the doubling of time, leaving the ratio unchanged.

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Practice MCQs for Class 9 Science Chapter 07 Work, Energy, And Simple Machines

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