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JKCET Work and Energy — practice questions — page 3

Explore 102 free Work and Energy questions in JKCET Physics. Open each question or exercise to read its content, reference answers and available explanation.

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Work and Energy questions and exercises with answers

Showing questions 61–90 of 102.

The maximum speed at which a car can round an unbanked circular turn of radius 150 m without skidding is (μs = 0.6, g = 10 m s⁻²):Read the answer and worked solution →For a 3 kg block connected over a frictionless pulley to a 20 kg trolley (μk = 0.04, g = 10 m s⁻²), the tension in the connecting string is:Read the answer and worked solution →A net force F = 6t newton (t in seconds) acts on a 2 kg body initially at rest. The speed of the body at t = 4 s is:Read the answer and worked solution →A block slides down a rough incline of 30° with coefficient of kinetic friction 0.2 (g = 10 m s⁻²). Its acceleration down the incline is:Read the answer and worked solution →A lift descends with a downward acceleration equal to g. The apparent weight of a passenger standing inside is:Read the answer and worked solution →A 0.2 kg ball strikes the floor vertically at 10 m s⁻¹ and rebounds at 8 m s⁻¹. The magnitude of the impulse imparted by the floor on the ball is:Read the answer and worked solution →The optimum (design) speed for a car on a frictionless road banked at 45° along a curve of radius 100 m is (g = 10 m s⁻²):Read the answer and worked solution →True or false: what Aristotle got wrongRead the answer and worked solution →Complete Newton's first lawRead the answer and worked solution →Which law is this?Read the answer and worked solution →MomentumRead the answer and worked solution →True or false: inertia and forceRead the answer and worked solution →Assertion and reasonRead the answer and worked solution →Two are true, one is notRead the answer and worked solution →Three of these are wrong. Find the one that holds.Read the answer and worked solution →Tap every statement the first law licensesRead the answer and worked solution →Flip and pair: name with contributionRead the answer and worked solution →Spot the one that does not belongRead the answer and worked solution →Order the historical argumentRead 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 →

Worked practice questions

The maximum speed at which a car can round an unbanked circular turn of radius 150 m without skidding is (μs = 0.6, g = 10 m s⁻²):

  1. 15 m s⁻¹
  2. 45 m s⁻¹
  3. 90 m s⁻¹
  4. 30 m s⁻¹
Show answer and solution

Correct answer: D. 30 m s⁻¹

On a level road friction provides the centripetal force: v_max = √(μs R g) = √(0.6×150×10) = √900 = 30 m s⁻¹, independent of mass.

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For a 3 kg block connected over a frictionless pulley to a 20 kg trolley (μk = 0.04, g = 10 m s⁻²), the tension in the connecting string is:

  1. 8.0 N
  2. 22.0 N
  3. 27.1 N
  4. 30.0 N
Show answer and solution

Correct answer: C. 27.1 N

Using a = 0.96 m s⁻² from the system equations, T = 3(g − a) = 3(10 − 0.96) = 27.1 N (equivalently T = 8 + 20a).

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A net force F = 6t newton (t in seconds) acts on a 2 kg body initially at rest. The speed of the body at t = 4 s is:

  1. 48 m s⁻¹
  2. 6 m s⁻¹
  3. 24 m s⁻¹
  4. 12 m s⁻¹
Show answer and solution

Correct answer: C. 24 m s⁻¹

Impulse = ∫₀⁴ 6t dt = 3t²|₀⁴ = 48 N s = Δp hence v = Δp/m = 48/2 = 24 m s⁻¹. Distractors drop the time-integration or the mass.

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