Asked in KMU MDCAT 2023 2023Moderate

A 200N force acts on 8 kg crate that starts from rest. At the instant the object has gone 2m, the rate at which the force is doing work is:

Correct answer: D. 2000 W

  • A. 2.5 W
  • B. 25 W
  • C. 75 W
  • D. 2000 W

Explanation

To find the rate at which the force is doing work (power), we first need to determine the velocity of the crate after it has moved 2 meters. Using Newton's second law, we can calculate the acceleration:F = ma200 N = 8 kg * aa = 25 m/s²Next, we use the kinematic equation to find the velocity after traveling 2m from rest:v² = u² + 2asv² = 0 + 2 * 25 m/s² * 2mv² = 100v = 10 m/sNow we can calculate the power using P = F * v:P = 200 N * 10 m/s = 2000 WThis explains why option D is correct. The other options are incorrect as they either miscalculate the power output or do not take into account the velocity of the crate after it has traveled the specified distance.

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About Power

Power is the rate at which work is done or energy is transferred, with average power calculated over a time interval and instantaneous power found from P = Fv when force and velocity are aligned. Work includes units, mechanical efficiency, and the distinction between power and total work or energy.

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