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24 April, 10:39

A student drops a 1.5 kg rock off of a 4.0 m tall bridge. The speed of the rock just before it hits the water below is 6 m/s. How much energy was lost due to air resistance?

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Answers (2)
  1. 24 April, 10:42
    0
    Energy due to air resistance = 31.8 Joules

    Explanation:

    According to the law of conservation of energy, energy can neither be created nor destroyed but can be transformed from one form to another

    Kinetic Energy + Energy due to air resistance = Potential energy ... (1)

    If there is no energy loss due to air resistance, potential energy = kinetic energy

    mass, m = 1.5 kg

    height, h = 4.0 m

    speed, v = 6 m/s

    Kinetic energy = 0.5 mv²

    Kinetic energy = 0.5 * 1.5 * 6²

    Kinetic energy = 27 Joules

    Potential Energy = mgh

    Potential energy = 1.5 * 9.8 * 4

    Potential energy = 58.8 Joules

    From equation (1)

    27 + Energy due to air resistance = 58.8

    Energy due to air resistance = 58.8 - 27

    Energy due to air resistance = 31.8 Joules
  2. 24 April, 10:45
    0
    Note:

    Air resistance in the way means not all of the potential energy can be converted to kinetic energy.

    Given:

    Mass = 1.5 kg

    D = 4 m

    Vf = 6 m/s

    Energy + KE = PE

    = (M * g * d) - (1/2 * M * V^2)

    = (1.5 * 9.8 * 4) - (1/2 * 1.5 * 6^2)

    = 58.8 - 27

    = 31.8 J
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