A 20.0 kg rock is sliding on a rough , horizontal surface at8.00 m/s and eventually stops due to friction .The coefficient ofkinetic friccti

Question

A 20.0 kg rock is sliding on a rough , horizontal surface at8.00 m/s and eventually stops due to friction .The coefficient ofkinetic fricction between the rock and the surface is 0.20
what average thermal power is produced as the rock stops?

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Ladonna 4 years 2021-09-03T14:04:19+00:00 1 Answers 40 views 0

Answers ( )

  1. thuthuy
    0
    2021-09-03T14:06:12+00:00
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    Answer:

    Therefore the average thermal power is = 19.61 W

    Explanation:

    Given that the mass of the rock = 20.0 kg

    initial velocity (u) = 8.00m/s

    Final velocity = 0

    Kinetic fiction (\mu_k) = 0.20.

    Friction force = Kinetic fiction× weight

                          =\mu_k mg

    Force = mass × acceleration

    \Rightarrow acceleration =\frac{Force}{mass}

                            =-\frac{\mu_kmg}{m}

                            =-\mu_kg

    To find the time , we use the the following formula,

    v=u+at

    Here a =-\mu_kg

    \Rightarrow 0=8+(-\mu_kg)t

    \Rightarrow 0.20 \times 9.8\times t=8

    ⇒t = 4.08 s

    Now,

    Thermal energy= work done by friction = change of kinetic energy

    The change of kinetic energy

    = \frac{1}{2} mu^2-\frac{1}{2} mv^2

    =\frac{1}{2}\times 20\times 8 -\frac{1}{2}\times 20\times 0

    =80 J

    Thermal energy=80 J

    Thermal power = Thermal energy per unit time

                              =\frac{80}{4.08} w

                             =19.61 W

    Therefore 19.61 W average thermal power is produced as the rock stops.

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