Energy Physics Example 4

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Example 4

medium
A 3 kg3 \text{ kg} rock at 15 m15 \text{ m} above the ground is moving at 4 m/s4 \text{ m/s}. What is its total mechanical energy? Use g=10 m/s2g = 10 \text{ m/s}^2.

Solution

  1. 1
    Kinetic energy: KE=12mv2=12(3)(16)=24 JKE = \frac{1}{2}mv^2 = \frac{1}{2}(3)(16) = 24 \text{ J}.
  2. 2
    Gravitational potential energy: PE=mgh=3×10×15=450 JPE = mgh = 3 \times 10 \times 15 = 450 \text{ J}.
  3. 3
    Total: E=KE+PE=24+450=474 JE = KE + PE = 24 + 450 = 474 \text{ J}.

Answer

E=474 JE = 474 \text{ J}
Total mechanical energy is the sum of kinetic and potential energy. At any point in the object's trajectory (ignoring friction), this total stays the same.

About Energy

The capacity to do work or cause change in a physical system, measured in joules (J).

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Example 2 medium

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Example 3 easy

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