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1. Work done by a force is defined as the product of force and:
A. Displacement in the direction of the force
B. Time taken
C. Mass of the object
D. Velocity of the object
Answer: A. Displacement in the direction of the force
Explanation: Work is calculated as the component of force acting along the direction of displacement, multiplied by the displacement.
2. The SI unit of work is the:
A. Joule
B. Newton
C. Watt
D. Pascal
Answer: A. Joule
Explanation: The joule (J) is the SI unit of work, equivalent to one newton-metre.
3. Work done is zero when the force and displacement are:
A. Perpendicular to each other
B. Parallel to each other
C. In the same direction
D. Equal in magnitude
Answer: A. Perpendicular to each other
Explanation: Since work = force × displacement × cos(θ), when the angle θ between them is 90°, cos(90°) = 0, making the work done zero.
4. The capacity of a body to do work is called its:
A. Energy
B. Power
C. Force
D. Momentum
Answer: A. Energy
Explanation: Energy is defined as the capacity or ability of a body to perform work.
5. The energy possessed by a body due to its motion is called:
A. Kinetic energy
B. Potential energy
C. Mechanical energy only
D. Chemical energy
Answer: A. Kinetic energy
Explanation: Kinetic energy is specifically the energy an object possesses because of its motion.
6. The energy possessed by a body due to its position or configuration is called:
A. Potential energy
B. Kinetic energy
C. Thermal energy
D. Electrical energy
Answer: A. Potential energy
Explanation: Potential energy is stored energy associated with an object's position, such as height above the ground, or its configuration.
7. The formula for kinetic energy of an object with mass m and velocity v is:
A. 1/2 mv²
B. mv²
C. mv
D. 1/2 mv
Answer: A. 1/2 mv²
Explanation: Kinetic energy is calculated using the formula (1/2) × mass × velocity squared.
8. The formula for gravitational potential energy at height h is:
A. mgh
B. 1/2 mv²
C. mgh²
D. mg/h
Answer: A. mgh
Explanation: Gravitational potential energy is calculated as mass × gravitational acceleration (g) × height (h).
9. The law of conservation of energy states that energy can neither be created nor destroyed, but can only be:
A. Transformed from one form to another
B. Increased over time
C. Decreased over time
D. Completely lost
Answer: A. Transformed from one form to another
Explanation: This fundamental law asserts that total energy remains constant, though it may change forms, such as from potential to kinetic.
10. The rate at which work is done is called:
A. Power
B. Energy
C. Force
D. Momentum
Answer: A. Power
Explanation: Power specifically measures how quickly work is performed, calculated as work done divided by time taken.
11. The SI unit of power is the:
A. Watt
B. Joule
C. Newton
D. Pascal
Answer: A. Watt
Explanation: The watt (W) is the SI unit of power, equivalent to one joule per second.
12. A collision in which both momentum and kinetic energy are conserved is called a/an:
A. Elastic collision
B. Inelastic collision
C. Perfectly inelastic collision
D. Non-conservative collision
Answer: A. Elastic collision
Explanation: In an elastic collision, both the total momentum and total kinetic energy of the system remain unchanged before and after collision.
13. A collision in which momentum is conserved but kinetic energy is not conserved is called a/an:
A. Inelastic collision
B. Elastic collision
C. Frictionless collision
D. Reversible collision
Answer: A. Inelastic collision
Explanation: In an inelastic collision, some kinetic energy is converted into other forms (like heat or sound), while momentum remains conserved.
14. In a perfectly inelastic collision, the colliding objects:
A. Stick together and move with a common velocity after collision
B. Bounce apart with equal speeds
C. Conserve all kinetic energy
D. Do not interact at all
Answer: A. Stick together and move with a common velocity after collision
Explanation: A perfectly inelastic collision results in the two objects combining and moving together with a shared final velocity.
15. The work-energy theorem states that the work done by the net force on an object equals the:
A. Change in its kinetic energy
B. Change in its potential energy only
C. Total momentum
D. Total power
Answer: A. Change in its kinetic energy
Explanation: The work-energy theorem directly relates the net work done on an object to the resulting change in its kinetic energy.
16. A force that does work independent of the path taken, depending only on initial and final positions, is called a:
A. Conservative force
B. Non-conservative force
C. Frictional force always
D. Applied force only
Answer: A. Conservative force
Explanation: Conservative forces, such as gravity, perform work that depends solely on the starting and ending positions, not the specific path.
17. Friction is generally classified as a:
A. Non-conservative force
B. Conservative force
C. Gravitational force
D. Elastic force
Answer: A. Non-conservative force
Explanation: Since the work done against friction depends on the path length travelled, friction is classified as a non-conservative force.
18. The total mechanical energy of a system remains constant if only:
A. Conservative forces are acting on it
B. Non-conservative forces are acting
C. External forces are removed entirely
D. Friction is present
Answer: A. Conservative forces are acting on it
Explanation: Mechanical energy conservation applies specifically when only conservative forces, like gravity, act on the system, with no energy loss to friction or other non-conservative forces.
19. When a spring is stretched or compressed, it stores energy known as:
A. Elastic potential energy
B. Kinetic energy
C. Gravitational potential energy
D. Thermal energy
Answer: A. Elastic potential energy
Explanation: Elastic potential energy is the specific type of stored energy resulting from the deformation (stretching or compressing) of an elastic object like a spring.
20. The formula for elastic potential energy stored in a spring with spring constant k and extension x is:
A. 1/2 kx²
B. kx
C. 1/2 kx
D. kx²
Answer: A. 1/2 kx²
Explanation: The elastic potential energy stored in a spring is calculated as one-half the spring constant multiplied by the square of its extension or compression.
21. The dot product used to calculate work done by a constant force is defined mathematically as:
A. W = F·s = Fs cos θ
B. W = F + s
C. W = F/s
D. W = Fs sin θ
Answer: A. W = F·s = Fs cos θ
Explanation: Work is calculated as the scalar (dot) product of force and displacement vectors, given by Fs cos θ, where θ is the angle between them.
22. If the angle between the applied force and displacement is 0°, the work done is:
A. Maximum, equal to Fs
B. Zero
C. Negative
D. Undefined
Answer: A. Maximum, equal to Fs
Explanation: When force and displacement are in the same direction (θ = 0°), cos(0°) = 1, resulting in maximum possible work being done.
23. If the angle between the applied force and displacement is 180°, the work done is:
A. Negative
B. Positive maximum
C. Zero
D. Undefined
Answer: A. Negative
Explanation: When force acts opposite to displacement (θ = 180°), cos(180°) = -1, resulting in negative work being done.
24. A machine that has an efficiency of 100% would mean:
A. All input energy is converted to useful output work with none lost
B. It requires no input energy
C. It produces infinite energy
D. It cannot function at all
Answer: A. All input energy is converted to useful output work with none lost
Explanation: 100% efficiency, though practically unachievable, would mean all supplied energy converts entirely into useful work with no losses.
25. The power delivered by a machine doing work W in time t is calculated as:
A. P = W/t
B. P = Wt
C. P = W + t
D. P = t/W
Answer: A. P = W/t
Explanation: Power is defined as the rate of doing work, calculated by dividing the total work done by the time taken.
26. If a body of mass 2 kg moves with a velocity of 3 m/s, its kinetic energy is:
A. 9 J
B. 6 J
C. 18 J
D. 3 J
Answer: A. 9 J
Explanation: KE = 1/2 × m × v² = 1/2 × 2 × 3² = 1/2 × 2 × 9 = 9 J.
27. In an elastic collision between two identical masses, where one is initially at rest, after collision:
A. The moving mass comes to rest, and the initially stationary mass moves with the original velocity
B. Both masses move together
C. Neither mass moves
D. The initially stationary mass remains at rest
Answer: A. The moving mass comes to rest, and the initially stationary mass moves with the original velocity
Explanation: This is a special result of elastic collisions between equal masses: complete transfer of velocity occurs between the two identical masses.
28. The concept of negative work is applicable when the force acts:
A. Opposite to the direction of displacement
B. In the same direction as displacement
C. Perpendicular to displacement
D. At exactly zero magnitude
Answer: A. Opposite to the direction of displacement
Explanation: When the applied force has a component opposing the motion's direction, the resulting work done is considered negative.
29. In the absence of air resistance, a ball thrown upward and falling back demonstrates the interconversion between:
A. Kinetic energy and potential energy
B. Only thermal energy
C. Only sound energy
D. Only chemical energy
Answer: A. Kinetic energy and potential energy
Explanation: As the ball rises, kinetic energy converts to potential energy, and this process reverses as it falls back down, illustrating mechanical energy conservation.
30. 1 horsepower (hp) is approximately equal to:
A. 746 watts
B. 1000 watts
C. 100 watts
D. 7460 watts
Answer: A. 746 watts
Explanation: The commonly used conversion factor states that 1 horsepower is approximately equal to 746 watts.
This page contains a chapter-wise objective practice set. Try the questions without checking the answer first, then use the explanation to understand the point you missed. The current page contains 30 questions, so you can practise in smaller sets when you are revising.
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