Power Physics Example 4

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Example 4

medium
Two cranes each lift a 500 kg500 \text{ kg} load 20 m20 \text{ m}. Crane A takes 50 s50 \text{ s} and Crane B takes 100 s100 \text{ s}. What is each crane's power output? Use g=10 m/s2g = 10 \text{ m/s}^2.

Solution

  1. 1
    Both do the same work: W=mgh=500×10×20=100,000 JW = mgh = 500 \times 10 \times 20 = 100{,}000 \text{ J}.
  2. 2
    Crane A: PA=100,00050=2000 WP_A = \frac{100{,}000}{50} = 2000 \text{ W}.
  3. 3
    Crane B: PB=100,000100=1000 WP_B = \frac{100{,}000}{100} = 1000 \text{ W}.

Answer

PA=2000 W,PB=1000 WP_A = 2000 \text{ W}, \quad P_B = 1000 \text{ W}
Both cranes do the same total work, but the faster crane has twice the power output. Power measures how quickly work is done, not how much work is done.

About Power

The rate at which work is done or energy is transferred, measured in watts (joules per second).

Learn more about Power →

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Example 1 easy

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Example 2 medium

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Example 3 easy

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