How much of JEE Main comes from Work Energy and Power?

JEEGenie estimates about 4% of JEE Main marks come from Work Energy and Power, based on recent papers. The share varies from year to year.

Which formulas matter most in Work Energy and Power?

The Work Energy and Power sheet on this page has 23 formula entries, starting with Work Done by a Constant Force, Work Done by a Variable Force, Kinetic Energy, Work-Energy Theorem, Conservative Force. Each one comes with when to use it and the trap to avoid.

What topics does Work Energy and Power cover for JEE?

Work Energy and Power covers Work Done by a Force, Kinetic and Potential Energy, Work-Energy Theorem, Conservation of Energy, Power, Collisions.

How should I revise Work Energy and Power before the exam?

Learn each formula together with its condition of use, read the trap listed beside it, then practise questions and review every mistake. The practice link on this page opens Work Energy and Power questions on JEEGenie.

How many previous-year questions are there on Work Energy and Power?

JEEGenie has 222 previous-year questions on Work Energy and Power, and this page shows a few with worked explanations.

Is practice on Work Energy and Power free on JEEGenie?

Sign-up is free and includes a 7-day Pro trial. After the trial, free accounts keep a limited daily quota.

Work Energy and Power for JEE Main & Advanced — formulas, what is asked, and traps

JEEGenie estimates about 4% of JEE Main marks come from Work Energy and Power. This page covers 23 formula entries, each with when to use it, what JEE asks and the traps. A common slip: Forgetting that work is zero if force and displacement are perpendicular ( $θ = 90^{\circ}$ ).

Key points to know

Work Done by a Constant Force. Work is the dot product of force and displacement vectors; only the component of force along displacement does work.
Work Done by a Variable Force. For a force varying with position, work is the integral of force over displacement, equal to area under F-x curve.
Kinetic Energy. Energy due to motion; equals half the product of mass and square of velocity.
Work-Energy Theorem. Net work done by all forces on a particle equals change in its kinetic energy.
Conservative Force. Work done by a conservative force is path-independent and equals negative change in potential energy.
Non-Conservative Force. Work done by non-conservative forces depends on path and dissipates mechanical energy (e.g., friction).
Potential Energy. Energy stored due to position or configuration in a conservative force field.
Conservation of Mechanical Energy. If only conservative forces do work, total mechanical energy (KE + PE) remains constant.
Power. Rate of doing work or transferring energy; scalar quantity.
Work Done by a Constant Torque (Rotational Work). In rotational motion, work is torque times angular displacement.
Rotational Kinetic Energy. Energy due to rotation; depends on moment of inertia and angular velocity.
Elastic and Inelastic Collisions (Energy Aspect). In elastic collisions, kinetic energy is conserved; in inelastic, some KE is lost.
Potential Energy Curve and Equilibrium. Stable equilibrium at minima of U(x); unstable at maxima; force is negative gradient.

Formula sheet

Name	Formula	When to use
Work Done by a Constant Force	$W = \vec{F} \cdot \vec{s} = F s \cos θ$	Use when force is constant and displacement is known; calculate work in mechanics problems.
Work Done by a Variable Force	$W = \int_{x_{i}}^{x_{f}} F (x) d x$	Use when force depends on position (e.g., spring force, non-uniform fields).
Kinetic Energy	$K = \frac{1}{2} m v^{2}$	Use to relate speed and mass in energy conservation or work-energy theorem.
Work-Energy Theorem	$W_{net} = Δ K = K_{f} - K_{i}$	Use to relate work and speed changes without needing acceleration details.
Conservative Force	$W_{c} = - Δ U$	Use to identify forces where potential energy can be defined (gravity, spring, electrostatic).
Non-Conservative Force	$W_{n c} = Δ E_{mech}$ (negative for dissipation)	Use when friction, air resistance, or applied forces are present; account for energy loss.
Potential Energy	$Δ U = - W_{c} = - \int \vec{F} \cdot d \vec{r}$	Use to simplify problems with conservative forces via energy conservation.
Gravitational Potential Energy	$U_{g} = m g h$	Use for objects near Earth's surface in energy conservation problems.
Spring Potential Energy	$U_{s} = \frac{1}{2} k x^{2}$	Use for springs, elastic strings, or any Hooke's law system.
Conservation of Mechanical Energy	$E_{mech} = K + U = constant$	Use for systems with only conservative forces (e.g., free fall, pendulum, spring-mass).
Power	$P = \frac{d W}{d t} = \vec{F} \cdot \vec{v}$	Use to compute energy transfer rate in engines, motors, or moving objects.
Using Work-Energy Theorem with Multiple Forces	$W_{gravity} + W_{spring} + W_{friction} + \dots = Δ K$	Use when multiple forces act, especially including non-conservative forces.
Solving with Conservation of Mechanical Energy	$K_{i} + U_{i} = K_{f} + U_{f}$	Use for frictionless systems with only conservative forces (e.g., pendulum, spring).
Work Done by Friction	$W_{friction} = - μ_{k} N d$ (where $d$ is path length)	Use when objects slide on surfaces with kinetic friction.
Variable Force: Spring Force	$W_{spring} = - \frac{1}{2} k (x_{f}^{2} - x_{i}^{2})$	Use for any Hooke's law spring in work-energy or conservation problems.
Work Done by a Constant Torque (Rotational Work)	$W = τ θ$ (for constant torque)	Use for rotational systems with constant torque (e.g., rotating pulleys).
Rotational Kinetic Energy	$K_{rot} = \frac{1}{2} I ω^{2}$	Use for rotating bodies, especially in rolling without slipping problems.
Energy Conservation in Rolling Motion	$m g h = \frac{1}{2} m v^{2} + \frac{1}{2} I ω^{2}$ with $v = ω R$	Use for objects rolling down inclines or on surfaces without slipping.
Elastic and Inelastic Collisions (Energy Aspect)	Elastic: $\sum K_{i} = \sum K_{f}$ ; Inelastic: $\sum K_{f} < \sum K_{i}$	Use to analyze collisions; check if KE is conserved to determine type.
Coefficient of Restitution	$e = \frac{v_{2} - v_{1}}{u_{1} - u_{2}}$	Use in collision problems to relate velocities and find energy loss.
Work-Energy for Systems with Internal Forces	$W_{ext} + W_{int} = Δ K_{system}$ (all internal forces); equivalently $W_{ext} + W_{int, nc} = Δ K + Δ U_{int}$ .	Use for multi-object systems with internal friction or springs.
Graphical Interpretation of Work	$W = \int F d x = Area under F (x) vs x$	Use when given a force-displacement graph to find work.
Potential Energy Curve and Equilibrium	$F = - \frac{d U}{d x}$	Use to analyze motion from potential energy graphs (e.g., diatomic molecules).

Open the Work Energy and Power formula page

What JEE asks

Work Done by a Constant Force. JEE often asks to compute work for forces at angles, or to identify zero-work scenarios (e.g., centripetal force).
Work Done by a Variable Force. JEE tests graphical interpretation: area under F-x curve gives work, often with spring or elastic forces.
Kinetic Energy. JEE often asks to find KE from work done or vice versa, especially in collisions.
Work-Energy Theorem. JEE frequently uses this to solve problems involving variable forces or multiple steps.
Conservative Force. JEE tests identification: e.g., gravity and spring force are conservative; friction is not.
Non-Conservative Force. JEE often asks to compute work done against friction or energy dissipated.
Potential Energy. JEE tests potential energy for gravity ( $m g h$ ) and springs ( $\frac{1}{2} k x^{2}$ ).
Gravitational Potential Energy. JEE often combines with kinetic energy to find speeds in free fall or inclined planes.
Spring Potential Energy. JEE tests energy conservation with springs, often in combination with gravity.
Conservation of Mechanical Energy. JEE frequently uses this to find speeds at different positions in roller coasters or pendulums.
Power. JEE tests instantaneous power from force and velocity, or average power over time.
Using Work-Energy Theorem with Multiple Forces. JEE often asks to find speed after sliding with friction or on a curved track.
Solving with Conservation of Mechanical Energy. JEE tests with objects sliding on frictionless tracks or oscillating springs.
Work Done by Friction. JEE often asks to compute energy lost due to friction on inclined planes or horizontal surfaces.
Variable Force: Spring Force. JEE tests spring-block systems, often with energy conservation to find compression or speed.
Work Done by a Constant Torque (Rotational Work). JEE may combine with rotational kinetic energy in advanced problems.
Rotational Kinetic Energy. JEE tests rolling objects on inclines using energy conservation including rotational KE.
Energy Conservation in Rolling Motion. JEE often asks to compare speeds of different shapes (sphere, cylinder) rolling down.
Elastic and Inelastic Collisions (Energy Aspect). JEE tests energy loss in inelastic collisions, often with coefficient of restitution.
Coefficient of Restitution. JEE often asks to find $e$ from given velocities or energy loss.
Work-Energy for Systems with Internal Forces. JEE tests energy loss in systems like blocks on rough surfaces or connected by springs.
Graphical Interpretation of Work. JEE often provides F-x graphs and asks for work done or energy changes.
Potential Energy Curve and Equilibrium. JEE tests identifying equilibrium points and turning points from U-x graphs.

Common traps

Forgetting that work is zero if force and displacement are perpendicular ( $θ = 90^{\circ}$ ). Work Done by a Constant Force
Forgetting to integrate with respect to the correct variable (e.g., time vs position). Work Done by a Variable Force
Using $m v^{2}$ instead of $\frac{1}{2} m v^{2}$ . Kinetic Energy
Applying only to conservative forces; it holds for all forces (including non-conservative). Work-Energy Theorem
Assuming all forces are conservative; friction is non-conservative. Conservative Force
Thinking non-conservative forces cannot do positive work; they can (e.g., pushing). Non-Conservative Force
Forgetting that only changes in potential energy are physically meaningful. Potential Energy
Forgetting that $h$ is measured from a chosen reference (usually ground). Gravitational Potential Energy
Forgetting the factor $\frac{1}{2}$ ; using $k x^{2}$ is wrong. Spring Potential Energy
Applying when non-conservative forces (friction) are present; then energy is not conserved. Conservation of Mechanical Energy
Using average power $P = W / t$ when instantaneous power is needed. Power
Double-counting work when using potential energy; either use work or potential energy, not both. Using Work-Energy Theorem with Multiple Forces
Forgetting to include all forms of potential energy (e.g., both gravitational and elastic). Solving with Conservation of Mechanical Energy
Using displacement instead of path length; friction work depends on distance traveled. Work Done by Friction

Topics in Work Energy and Power

Work Done by a Force
Kinetic and Potential Energy
Work-Energy Theorem
Conservation of Energy
Power
Collisions

Previous-year questions on Work Energy and Power

JEEGenie has 222 previous-year questions on Work Energy and Power. A few worked examples follow.

Year	Questions
2026	13
2025	13
2024	19
2023	25
2022	14
2021	23
2020	12
2019	12
2018	6
2017	7
2016	6
2015	1
2014	6
2013	7
2012	3
2011	1
2010	1
2009	1
2008	4
2007	2
2006	4
2005	4
2004	5
2003	4
2002	4
2001	1
2000	1
1999	1
1998	2
1997	2
1994	2
1991	1
1990	1
1988	1
1987	2
1985	2
1984	1
1983	3
1981	1
1980	3
1979	1

Question 1 medium

A spherical ball of mass 2 kg falls from a height of 10 m and is brought to rest after penetrating 10 cm into sand. The average force exerted by sand on the ball is _________ N. (Take

g = 10 m / s^{2}

)

1980
2020
2000
1000

Answer: B

Explanation. 1. Let the ball fall from height

h = 10 m

and penetrate a distance

x = 10 cm = 0.1 m

into the sand. 2. The ball starts from rest and comes to rest, so the net change in kinetic energy is zero:

Δ K = 0

. 3. Work done by gravity over the total distance

(h + x)

is positive:

W_{g} = m g (h + x) = 2 \times 10 \times (10 + 0.1) = 202 J

. 4. Work done by the average resistive force

F

of the sand is negative:

W_{sand} = - F \cdot x = - F \times 0.1

. 5. By the Work-Energy Theorem:

W_{g} + W_{sand} = Δ K = 0 \Rightarrow 202 - 0.1 F = 0

. 6. Solving:

F = \frac{202}{0.1} = 2020 N

. 7. Therefore, the average force exerted by the sand is

2020 N

. **Answer: B) 2020**

From NTA/IIT papers: JEE Main 2026 · 2 Apr Shift 2

Question 2 easy

A particle is released from height

S

above the surface of the earth. At certain height its kinetic energy is three times its potential energy. The height from the surface of the earth and the speed of the particle at that instant are respectively.

$\frac{S}{4}, \frac{3 g S}{2}$
$\frac{S}{2}, \frac{3 g S}{2}$
$\frac{S}{4}, \sqrt{\frac{3 g S}{2}}$
$\frac{S}{2}, \sqrt{\frac{3 g S}{2}}$

Answer: C

Explanation. Let total height from release point be

S

. At height

h

above ground, potential energy

U = m g h

and kinetic energy

K = \frac{1}{2} m v^{2}

. Given

K = 3 U

, so:

\frac{1}{2} m v^{2} = 3 m g h \Rightarrow v^{2} = 6 g h .

By conservation of energy from release:

m g S = m g h + \frac{1}{2} m v^{2} = m g h + 3 m g h = 4 m g h .

Thus

h = \frac{S}{4}

. Then

v^{2} = 6 g \cdot \frac{S}{4} = \frac{3 g S}{2}

, so

v = \sqrt{\frac{3 g S}{2}}

. The answer is option C.

From NTA/IIT papers: JEE Main 2025 · 3 Apr Shift 1

Question 3 easy

If a rubber ball falls from a height

h

and rebounds upto the height of

h / 2

. The percentage loss of total energy of the initial system as well as velocity ball before it strikes the ground, respectively, are :

$50 %, \sqrt{2 g h}$
$50 %, \sqrt{g h}$
$50 %, \sqrt{\frac{gh}{2}}$
$40 %, \sqrt{2 g h}$

Answer: A

Explanation. The ball is dropped from height

h

, so its initial total mechanical energy (taking ground as reference) is purely potential energy:

E_{i} = m g h

After rebounding, the ball reaches height

h / 2

, so the total mechanical energy after the bounce is:

E_{f} = m g (\frac{h}{2}) = \frac{m g h}{2}

Percentage loss in total energy:

% loss = \frac{E_{i} - E_{f}}{E_{i}} \times 100 = \frac{m g h - \frac{m g h}{2}}{m g h} \times 100 = \frac{\frac{m g h}{2}}{m g h} \times 100 = 50 %

Velocity of the ball just before it strikes the ground (using energy conservation from height

h

\frac{1}{2} m v^{2} = m g h v = \sqrt{2 g h}

Both results match option (A):

50 %, \sqrt{2 g h}

From NTA/IIT papers: JEE Main 2024 · 4 Apr Shift 1

Question 4 medium

A particle of mass

10 g

moves in a straight line with retardation

2 x

, where

x

is the displacement in SI units. Its loss of kinetic energy for above displacement is

{(\frac{10}{x})}^{- n}

J. The value of

n

will be __________

Answer: 2

Explanation. F=ma => F=0.01*2x; Work done = integral(Fdx) = integral(0.02x dx) = 0.01

x^{2}

= 10^-2

x^{2}

J. Therefore, n=2

From NTA/IIT papers: JEE Main 2023 · 6 Apr Shift 1

Frequently asked questions

How much of JEE Main comes from Work Energy and Power?: JEEGenie estimates about 4% of JEE Main marks come from Work Energy and Power, based on recent papers. The share varies from year to year.
Which formulas matter most in Work Energy and Power?: The Work Energy and Power sheet on this page has 23 formula entries, starting with Work Done by a Constant Force, Work Done by a Variable Force, Kinetic Energy, Work-Energy Theorem, Conservative Force. Each one comes with when to use it and the trap to avoid.
What topics does Work Energy and Power cover for JEE?: Work Energy and Power covers Work Done by a Force, Kinetic and Potential Energy, Work-Energy Theorem, Conservation of Energy, Power, Collisions.
How should I revise Work Energy and Power before the exam?: Learn each formula together with its condition of use, read the trap listed beside it, then practise questions and review every mistake. The practice link on this page opens Work Energy and Power questions on JEEGenie.
How many previous-year questions are there on Work Energy and Power?: JEEGenie has 222 previous-year questions on Work Energy and Power, and this page shows a few with worked explanations.
Is practice on Work Energy and Power free on JEEGenie?: Sign-up is free and includes a 7-day Pro trial. After the trial, free accounts keep a limited daily quota.