Is Work, Energy and Power part of the EAPCET Physics syllabus?

Yes. Work, Energy and Power is taught in Intermediate first year Physics, and the EAPCET Engineering syllabus is based on the Intermediate first- and second-year syllabus. Check the official notification each year for any changes.

How many Physics questions are there in EAPCET?

40 of the 160 questions in the Engineering paper are Physics, spread across 30 chapters.

What mistakes do students make in Work, Energy and Power?

Conserving kinetic energy in an inelastic collision — only momentum is conserved there. Writing the work done in stretching a spring from x₁ to x₂ as ½k(x₂ − x₁)² — the correct value is ½k(x₂² − x₁²). Taking the work done by friction or by a braking force as positive — it opposes the motion, so it is negative. Adding work done by the centripetal force in circular motion — it is perpendicular to the velocity, so it does zero work.

EAPCET Physics · Intermediate first year

Work, Energy and Power

Work, Energy and Power covers work done by forces, kinetic and potential energy, the work–energy theorem, power and collisions.

Subject: Physics
Taught in: Intermediate first year
Physics in the paper: 40 of 160 questions

Key formulas and results

$W = \vec{F} \cdot \vec{s} = Fs\cos\theta$
Work–energy theorem: $W_{\text{net}} = \Delta\text{KE}$
Potential energy near the earth $= mgh$ ; of a spring $= \tfrac{1}{2}kx^{2}$
$P = \frac{W}{t} = \vec{F} \cdot \vec{v}$
In a 1D elastic collision of equal masses, the velocities are exchanged
Work by a variable force: $W = \int \vec{F} \cdot d\vec{r}$ = area under the force–displacement graph
Force from potential energy: $F = -\frac{dU}{dx}$
Body driven from rest at constant power $P$ : $v = \sqrt{2Pt/m}$ , $\text{KE} = Pt$ , distance $\propto t^{3/2}$
Work to pull a block slowly up a rough incline of height $h$ and base length $l$ : $W = mg(h + \mu l)$
Vertical circle (string length $l$ ) with the least speed: $\sqrt{gl}$ at the top, $\sqrt{3gl}$ at the side, $\sqrt{5gl}$ at the bottom; tension 0, $3mg$ and $6mg$ there
Pendulum released from angle $\theta$ : speed at the lowest point $v = \sqrt{2gl(1 - \cos\theta)}$
Coefficient of restitution: $e = \frac{v_{2} - v_{1}}{u_{1} - u_{2}}$ = speed of separation / speed of approach
Ball dropped from height $h$ with restitution $e$ : total distance $h\,\frac{1 + e^{2}}{1 - e^{2}}$ ; total time $\sqrt{\frac{2h}{g}}\cdot\frac{1 + e}{1 - e}$

What this chapter covers

Work done by constant and variable forces
Kinetic energy and the work–energy theorem
Potential energy
Conservation of mechanical energy
Power
Collisions

How it is usually asked

Work by a variable force
Elastic and inelastic collisions
Power calculations
Conservation of energy

Understanding Work, Energy and Power

Work is done when a force has a component along the displacement, W = Fs cos θ. It is a scalar and can be positive, negative or zero: friction usually does negative work, and a force perpendicular to the motion, such as the centripetal force, does none. For a variable force, work is the area under the force–displacement graph.

The work–energy theorem says the net work done on a body by all the forces acting on it equals its change in kinetic energy. When only conservative forces such as gravity and spring forces act, the total mechanical energy (kinetic plus potential) stays constant, so speeds at different heights can be found without knowing the forces or the time. Power is the rate of doing work, P = F · v.

In every collision of an isolated system, linear momentum is conserved. Kinetic energy is also conserved only in elastic collisions; in a perfectly inelastic collision the bodies stick together and the loss of kinetic energy is greatest. EAPCET questions often combine both ideas, for example finding the common velocity from momentum conservation and then the energy lost from the kinetic energies before and after.

Worked example

EAPCET-style question

A body of mass 2 kg moving at 6 m/s collides with and sticks to a body of mass 1 kg at rest. The loss of kinetic energy in the collision is

(1)12 J
(2)24 J
(3)36 J
(4)0 J

Solution

Momentum is conserved: $2 \times 6 = (2 + 1)v$ , so $v = 4\ \text{m/s}$ .
Initial KE $= \tfrac{1}{2} \times 2 \times 6^{2} = 36\ \text{J}$ .
Final KE $= \tfrac{1}{2} \times 3 \times 4^{2} = 24\ \text{J}$ .
Loss of KE $= 36 - 24 = 12\ \text{J}$ .

Answer: 12 J

Shortcuts and results to remember

A ball that rebounds with restitution $e$ loses $(1 - e^{2}) \times 100\,\%$ of its kinetic energy in each bounce.
Work to stretch a spring from $x_{1}$ to $x_{2}$ is $\tfrac{1}{2}k\left(x_{2}^{2} - x_{1}^{2}\right)$ ; if stretching by $x$ takes $W$ , stretching by a further $x$ takes $3W$ .
Oblique collision with a fixed surface: $e = \frac{\tan\alpha}{\tan\beta}$ , where $\alpha$ and $\beta$ are the angles with the normal before and after impact.
When a light ball hits a very heavy moving body, the heavy body’s velocity stays the same; use $e = \text{separation}/\text{approach}$ to get the ball’s velocity.
Ballistic pendulum: a bullet of mass $m$ and speed $u$ embedding in a block $M$ raises it by $h = \frac{(mu)^{2}}{2g(M + m)^{2}}$ .

Common mistakes to avoid

Conserving kinetic energy in an inelastic collision — only momentum is conserved there.
Writing the work done in stretching a spring from x₁ to x₂ as ½k(x₂ − x₁)² — the correct value is ½k(x₂² − x₁²).
Taking the work done by friction or by a braking force as positive — it opposes the motion, so it is negative.
Adding work done by the centripetal force in circular motion — it is perpendicular to the velocity, so it does zero work.

How to prepare it

When forces are messy, an energy method usually reaches the answer in fewer steps.

Once the formulas feel familiar, test them the way the exam does: practise Work, Energy and Power questions chapter-wise, then attempt a full previous year paper to see whether it holds up under a 3-hour timer.

Related Physics chapters

See every chapter in the EAPCET Physics syllabus.

Practise Work, Energy and Power chapter-wise

Chapter-wise quizzes show exactly which topics in this chapter you still get wrong — before a full paper does.

Frequently asked questions

Is Work, Energy and Power part of the EAPCET Physics syllabus?: Yes. Work, Energy and Power is taught in Intermediate first year Physics, and the EAPCET Engineering syllabus is based on the Intermediate first- and second-year syllabus. Check the official notification each year for any changes.
How should I prepare Work, Energy and Power for EAPCET?: When forces are messy, an energy method usually reaches the answer in fewer steps.
How many Physics questions are there in EAPCET?: 40 of the 160 questions in the Engineering paper are Physics, spread across 30 chapters.
What mistakes do students make in Work, Energy and Power?: Conserving kinetic energy in an inelastic collision — only momentum is conserved there. Writing the work done in stretching a spring from x₁ to x₂ as ½k(x₂ − x₁)² — the correct value is ½k(x₂² − x₁²). Taking the work done by friction or by a braking force as positive — it opposes the motion, so it is negative. Adding work done by the centripetal force in circular motion — it is perpendicular to the velocity, so it does zero work.