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    A particle of mass 3kg falls from rest at a height of 5m above a horizontal plane. It rebounds to a height 3m. Find the impulse exerted on the particle by the plane.

    So this question seems easy but I keep getting the wrong answer. The first method was to use SUVAT with s=2 (because the displacement is 2) u=0 and a=9.8. Using SUVAT equation I found v to be 6.26 then I found impulse which gave me -18.9.
    This was wrong so I tried to do two separate SUVAT equations one for when it hit the floor to get u= - 9.89 for when it hit the floor and rebounded so I got v=6.26 then subbed it into the impulse equation to get around 48 which is not the answer they asked for.
    The answer is 52.7 by the way.
    Any help would be appreciated.

    Use suvat to work out the speed just before it hits the ground and use that as your intial. Then work out the speed just after the collision by using mhg=1/2mv^s, where h=3.
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Updated: February 20, 2018

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