Sam asked in Science & MathematicsMathematics · 2 months ago

A 60 kg skateboard rides towards a hill with a speed of 8 m/s?

Calculate their kinetic energy.

If they ride up the hill, what will their total energy be at the midway point? 

If they reach the top of the hill with a speed of 4 m/s, how high is the hill?

1 Answer

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  • 2 months ago

    1) KE = ½mV² = ½60•8² = 30•64 = 1920 J

    2) need height of hill

    3) KE at top = ½60•4² = 30•16 = 480 J

    KE lost = 1920–480 = 1440 J

    that is equal to PE at top of hill

    PE = mgh = 1440 = 60•9.8•h

    h = 2.45 m

    back to 2:

    half way is 1.22 m

    PE at that point is mgh = 60•9.8•1.22 = 717 J

    lost energy = 1920 – 717 = 1203 J, which is KE

    KE = ½mV² = ½60•V² = 1203

    V² = 1203/(30) 

    V = 6.33 m/s

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