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JEE Main Work and Energy — practice questions

Explore 30 free Work and Energy questions in JEE Main Physics. Open each question or exercise to read its content, reference answers and available explanation.

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Work, Energy and Power: quick revision

Work connects force to a change in kinetic energy. Account for every force when using the work–energy theorem. Mechanical energy is conserved when only conservative forces do work; friction may transfer it into thermal energy.

Key ideas and when to use them

  • Constant-force work: $W=Fd\cos\theta$.
  • $K=\tfrac12mv^2$ and $W_{\rm net}=\Delta K$.
  • Ideal spring energy: $U=\tfrac12kx^2$; power is the rate of doing work.

Common mistakes

  • Use the angle between force and displacement, not an unrelated angle in the diagram.
  • Conservation of total energy does not imply conservation of mechanical energy.

Three worked examples

Example 1: A constant 12 N force acts at 60° to a displacement of 5 m. Find its work.
  1. Use the force component along displacement.
  2. $W=12\times5\times\cos60^\circ$.

30 J

Example 2: Find the kinetic energy of a 2 kg object moving at 3 m/s.
  1. Square the speed before multiplying.
  2. $K=\tfrac12\times2\times3^2$.

9 J

Example 3: An ideal spring of stiffness 200 N/m is compressed 0.10 m. Find its stored energy.
  1. Measure compression from the unstretched position.
  2. $U=\tfrac12\times200\times0.10^2$.

1 J

Qallery AI-assisted study notes and original examples. Further reading: NCERT Physics — Work, Energy and Power.

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Work and Energy questions and exercises with answers

Showing questions 1–30 of 30.

The SI unit of work and energy is the:Read the answer and worked solution →The joule is named after the physicist:Read the answer and worked solution →James Prescott Joule lived from 1811 until:Read the answer and worked solution →Power is measured in which SI unit:Read the answer and worked solution →One watt is equal to:Read the answer and worked solution →The unit of power is named after:Read the answer and worked solution →James Watt was one of the innovators of the:Read the answer and worked solution →In which century did James Watt do that work?Read the answer and worked solution →One horse-power is equal to:Read the answer and worked solution →Power is which kind of physical quantity?Read the answer and worked solution →A 100 watt bulb left on for 10 hours uses:Read the answer and worked solution →100 watts running for 10 hours gives how many watt hours?Read the answer and worked solution →Horse-power is still used to describe the output of:Read the answer and worked solution →You most often meet the watt when buying:Read the answer and worked solution →A force from which a potential energy can be derived is called:Read the answer and worked solution →The unit of potential energy is the same as that of:Read the answer and worked solution →In an inelastic collision, the final kinetic energy is:Read the answer and worked solution →The scalar product of two vectors gives a:Read the answer and worked solution →Which theorem links the work done with the change in kinetic energy?Read the answer and worked solution →The dimensions of power are:Read the answer and worked solution →Work and energy are measured in the same:Read the answer and worked solution →In an elastic collision of two bodies, what is conserved?Read the answer and worked solution →Match each unit to what it measuresRead the answer and worked solution →Work out the power numbersRead the answer and worked solution →True or false on work and energyRead the answer and worked solution →Elastic or inelastic collisionRead the answer and worked solution →Unit of whatRead the answer and worked solution →Fill the gaps on work and powerRead the answer and worked solution →Quick picks on work and energyRead the answer and worked solution →Spot the one that does not fitRead the answer and worked solution →

Worked practice questions

The SI unit of work and energy is the:

  1. Joule
  2. Jolt
  3. Joist
  4. Joust
Show answer and solution

Correct answer: A. Joule

1. Work and energy share the same unit. 2. That unit is the joule. 3. So the correct answer is joule. _Source: syllabus Physics Part I, Ch 6 'Work, Energy and Power'_

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The joule is named after the physicist:

  1. James Dewar
  2. James Joule
  3. James Watt
  4. James Clerk
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Correct answer: B. James Joule

1. The unit honours a British physicist. 2. It is named after James Prescott Joule. 3. So the correct answer is James Joule. _Source: syllabus Physics Part I, Ch 6 'Work, Energy and Power'_

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James Prescott Joule lived from 1811 until:

  1. 1869
  2. 1879
  3. 1859
  4. 1889
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Correct answer: A. 1869

1. His dates are given alongside the unit. 2. He lived from 1811 to 1869. 3. So the correct answer is 1869. _Source: syllabus Physics Part I, Ch 6 'Work, Energy and Power'_

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