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JEE Main Work, Energy and Power — practice questions — page 2

Explore 64 free Work, Energy and Power 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 questions and exercises with answers

Showing questions 31–60 of 64.

As per your syllabus, the unit kilowatt-hour (kWh) measures which physical quantity?Read the answer and worked solution →As per your syllabus, a 1800 kg elevator going up at 2 m/s against 4000 N friction needs minimum motor power approximately which?Read the answer and worked solution →As per your syllabus, + Summary, the dimensions of POWER are which?Read the answer and worked solution →As per your syllabus, an ELASTIC collision conserves which two quantities?Read the answer and worked solution →As per your syllabus, in an INELASTIC collision, which quantity is conserved (and which is not)?Read the answer and worked solution →As per your syllabus, eqn 5.22, in a COMPLETELY inelastic 1D collision (mass m₁ at v₁ hits m₂ at rest), the common final velocity is which?Read the answer and worked solution →As per your syllabus, eqn 5.26 / 5.27, in an ELASTIC 1D collision of m₁ (v₁) with m₂ (at rest), the final velocity v_{1f} is which?Read the answer and worked solution →As per your syllabus, (2D elastic between EQUAL masses, one at rest), the two final velocities make which angle with each other?Read the answer and worked solution →As per your syllabus, two cars colliding and locking together (no rebound) is an example of which collision type?Read the answer and worked solution →As per your syllabus, during the collision interval itself, conservation of momentum holds at which moments?Read the answer and worked solution →As per your syllabus, how many conservation equations does linear momentum yield in 3D?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 →

Worked practice questions

As per your syllabus, the unit kilowatt-hour (kWh) measures which physical quantity?

  1. Power
  2. Voltage
  3. Energy
  4. Force
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Correct answer: C. Energy

Your syllabus: kWh = power × time = energy. Used in electricity bills. 1 kWh = 3.6 × 10⁶ J.

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As per your syllabus, a 1800 kg elevator going up at 2 m/s against 4000 N friction needs minimum motor power approximately which?

  1. 8 kW
  2. 100 kW
  3. 17.6 kW
  4. 44.3 kW
Show answer and solution

Correct answer: D. 44.3 kW

syllabus Ex 5.10: F_motor = m g + f = 1800·9.8 + 4000 = 21640 N. P = F·v = 21640 × 2 ≈ 43.3 kW ≈ 44.3 kW.

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As per your syllabus, + Summary, the dimensions of POWER are which?

  1. [M L² T⁻³]
  2. [M L T⁻²]
  3. [M L T⁻¹]
  4. [M L² T⁻²]
Show answer and solution

Correct answer: A. [M L² T⁻³]

Your syllabus: power = energy / time = [M L² T⁻²]/[T] = [M L² T⁻³]. SI unit watt.

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