WORK, ENERGY AND POWER-True/False

Work, Energy and Power forms the cornerstone of classical mechanics in NCERT Class XI Physics Chapter 5, introducing students to fundamental concepts that bridge Newton's laws with modern energy-based problem-solving approaches. This carefully curated set of 25 True/False questions progresses systematically from basic definitional understanding to advanced Engineering Entrance level applications, testing conceptual clarity across work-energy theorem, conservative forces, potential energy functions, collision dynamics, and power calculations. Perfect for CBSE board preparation, JEE Main/Advanced revision, and competitive exam practice, these questions emphasize common misconceptions (like porter's work, variable force applications) while reinforcing critical relationships such as W_{net}=\Delta K, mechanical energy conservation under ideal conditions, and the distinction between elastic/inelastic collisions. Each statement includes precise explanations with MathJax-rendered equations, ensuring complete conceptual mastery from Class XI textbook level to IIT-JEE analytical depth.

Continue Reading →
Maths

TRIGONOMETRIC FUNCTIONS-Exercise 3.2

Exercise • Jan 2026

Trigonometric Functions form a crucial foundation of higher mathematics and play a vital role in physics, engineering, astronomy, and real-life proble...

Continue Reading →
Exercise
Maths

TRIGONOMETRIC FUNCTIONS-Exercise 3.1

Exercise • Jan 2026

Trigonometric Functions form a crucial foundation of higher mathematics and play a vital role in physics, engineering, astronomy, and real-life proble...

Continue Reading →
Exercise

WORK, ENERGY AND POWER

by Academia Aeternum

1. If a constant force acts on a body and there is no displacement, then the work done by the force is zero.
2. Work done by a force can be positive, negative or zero.
3. Kinetic energy of a body depends only on its speed and not on the direction of motion.
4. A body can possess energy even when its mechanical work per second (power) is zero.
5. The SI unit of work and the SI unit of energy are the same.
6. If a force is always perpendicular to the instantaneous displacement of a particle, then the work done by the force is zero.
7. When a body falls freely under gravity in vacuum, the loss in potential energy is equal to the gain in kinetic energy at every instant (neglecting relativistic effects).
8. A porter walking on a level road with a load on his head does positive work against gravity.
9. The area under a force–displacement graph represents the work done by that force.
10. If the net work done on a particle during its motion is zero, then its speed must remain constant.
11. Power is defined as the work done per unit time, so it must always be constant for a given process.
12. A conservative force is one for which the work done between two points depends only on the path taken.
13. The work done by all conservative forces over any closed path is zero.
14. In presence of non-conservative forces (like friction), the total mechanical energy of a system is always conserved.
15. A satellite moving in a perfectly circular orbit around the Earth has constant kinetic energy and constant gravitational potential energy.
16. For a body attached to an ideal spring obeying Hooke's law, the potential energy stored in the spring is proportional to the square of its extension.
17. A body can have non-zero momentum but zero kinetic energy in classical mechanics.
18. In an elastic collision between two particles, both kinetic energy and linear momentum of the system are conserved.
19. In an inelastic collision, total mechanical energy of the system decreases, but total linear momentum of the system can still remain conserved.
20. A heavier body always has more kinetic energy than a lighter body if both have the same linear momentum.
21. If the net external work done on a system of particles is zero, then the velocity of the centre of mass of the system must remain constant.
22. A variable force whose magnitude depends on position can never be treated using the work-energy theorem.
23. For a particle subjected only to a one-dimensional conservative force, the motion can be described by imagining the particle sliding in an effective potential energy curve.
24. The maximum speed of a particle executing vertical motion attached to a spring (neglecting air resistance) occurs at the extreme positions where its potential energy is maximum.
25. In a central gravitational field, a bound orbit with total mechanical energy just less than zero corresponds to a nearly parabolic trajectory, which is highly sensitive to small changes in energy.

Frequently Asked Questions

Work is said to be done when a force produces displacement in the direction of the force.

Work = Force × Displacement × cos?

Because it has magnitude only and no direction.

Work is positive when force and displacement are in the same direction.

Work is negative when force acts opposite to displacement.

Work is zero when displacement is zero or force is perpendicular to displacement.

Centripetal force in uniform circular motion does zero work.

A force whose magnitude or direction changes with displacement.

By finding the area under the force–displacement graph.

Energy is the capacity to do work.

Joule (J).

The sum of kinetic energy and potential energy.

Energy possessed by a body due to its motion.

KE = ½ mv²

Mass of the body and square of its velocity.

Energy possessed by a body due to its position or configuration.

Energy due to height in a gravitational field.

PE = mgh

Energy stored in a stretched or compressed elastic body.

Force is directly proportional to extension within elastic limit.

PE = ½ kx²

A force whose work is path independent.

Gravitational force, spring force.

A force whose work depends on path followed.

Friction, air resistance.

Net work done equals change in kinetic energy.

W = ?KE

It provides an alternative method to solve motion problems.

Energy can neither be created nor destroyed, only transformed.

When only conservative forces act.

When non-conservative forces like friction act.

Freely falling body under gravity.

Conversion of energy from one form to another.

Electrical to mechanical in motors.

Rate of doing work.

P = Work / Time

Power at a particular instant.

P = F · v

Watt (W).

A non-SI unit of power (1 hp ˜ 746 W).

Commercial unit of electrical energy.

Energy.

Ratio of useful output energy to input energy.

Efficiency = (Output/Input) × 100%

Due to energy losses like heat and friction.

It converts mechanical energy into heat.

Because it is perpendicular to velocity.

Distance covered before a moving body comes to rest due to braking.

Work–energy theorem.

It links kinematics and dynamics and is widely used in numericals.

Recent posts

    Important Links

    Core Concepts & Fundamentals
    Core Concepts & Fundamentals
    MCQ Practice
    MCQ Practice
    Textbook Exercises
    Textbook Exercises
    Q&A Discussion
    Q&A Discussion
    Read More
    Read More
    Explore Website
    Explore Website

    Leave Your Message & Comments