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UPCET / UPSEE Work, Energy and Power — practice questions

Explore 27 free Work, Energy and Power questions in UPCET / UPSEE Physics. Open each question or exercise to read its content, reference answers and available explanation.

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Work, Energy and Power questions and exercises with answers

Showing questions 1–27 of 27.

Work done by a constant force $\vec{F}$ when the body moves through displacement $\vec{s}$ is:Read the answer and worked solution →The kinetic energy of a body of mass $m$ moving with speed $v$ is:Read the answer and worked solution →The elastic potential energy stored in a spring of spring constant $k$ when stretched by displacement $x$ is:Read the answer and worked solution →The work-energy theorem states that the net work done on a body equals:Read the answer and worked solution →Complete the work-energy theoremRead the answer and worked solution →True or false: conservative forcesRead the answer and worked solution →Conservative or not?Read the answer and worked solution →Reading the theoremRead the answer and worked solution →Assertion and reasonRead the answer and worked solution →Two are true, one is notRead the answer and worked solution →Tap every test for a conservative forceRead the answer and worked solution →Order the reasoning: from work to speedRead the answer and worked solution →Flip and pair: term with meaningRead the answer and worked solution →Spot the one that does not belongRead the answer and worked solution →True or false: energy bookkeepingRead the answer and worked solution →Speeds up, slows down, or neither?Read the answer and worked solution →Applying the work-energy theoremRead the answer and worked solution →True or false: potential energyRead the answer and worked solution →Kinetic or potential?Read the answer and worked solution →Tap every statement true of a closed pathRead the answer and worked solution →Spot the one that does not belongRead the answer and worked solution →Assertion and reason: energyRead the answer and worked solution →Complete the potential energy relationRead the answer and worked solution →Flip and pair: quantity with what it tracksRead the answer and worked solution →Two are true, one is notRead the answer and worked solution →Order the reasoning: why a pendulum keeps swingingRead the answer and worked solution →Conservative or not, in practiceRead the answer and worked solution →

Worked practice questions

Work done by a constant force $\vec{F}$ when the body moves through displacement $\vec{s}$ is:

  1. $W = F + s$
  2. $W = F s \cos\theta$
  3. $W = F s \sin\theta$
  4. $W = F / s$
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Correct answer: B. $W = F s \cos\theta$

Work is defined as $W = \vec{F} \cdot \vec{s} = F s \cos\theta$, where $\theta$ is the angle between $\vec{F}$ and $\vec{s}$. Work is maximum ($Fs$) when force and displacement are parallel and zero when they are perpendicular ($\cos 90° = 0$). Negative work happens when force opposes motion (e.g. friction).

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The kinetic energy of a body of mass $m$ moving with speed $v$ is:

  1. $mv$
  2. $\dfrac{1}{2} m v^2$
  3. $m v^2$
  4. $\dfrac{1}{2} m v$
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Correct answer: B. $\dfrac{1}{2} m v^2$

Kinetic energy: $KE = \tfrac{1}{2} m v^2$. Notice the factor of $\tfrac{1}{2}$ and the $v^2$ dependence. The quadratic dependence is why a car at 60 km/h has four times the kinetic energy of the same car at 30 km/h, not twice. Stopping distance also scales as $v^2$ for the same brakes.

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The elastic potential energy stored in a spring of spring constant $k$ when stretched by displacement $x$ is:

  1. $kx$
  2. $\dfrac{1}{2} k x^2$
  3. $k x^2$
  4. $\dfrac{1}{2} k^2 x$
Show answer and solution

Correct answer: B. $\dfrac{1}{2} k x^2$

Force needed to stretch a spring by $x$ is $F = kx$ (Hooke's law). Work done in stretching from 0 to $x$: $U = \int_0^x kx' \, dx' = \dfrac{1}{2} k x^2$. The $\tfrac{1}{2}$ shows up because force grows linearly during the stretch — average force is $kx/2$, total work is $kx/2 \cdot x = \tfrac{1}{2} k x^2$. Option A ($kx$) is the *force*, not the energy.

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