Basic SUVAT stuff


    Rep:
    A bullet is fired horizontally at a speed of 200m/s at a target which is 100m away. Ignoring air resistance calculate how far the bullet has fallen when it hits the target.

    I used
    average v=s/t
    200=100/t
    200t=100
    t=100/200
    t=0.5s

    then I said gravity was 9.81m/s/s and so i did
    t*gravity = distance travelled down
    0.5*9.81= 4.905m

    The answers said it was 1.2m travelled down. How do you get there?

    Thanks in advance

    Rep:
    Where do you get your t*gravity = distance from

    s=ut +0.5at^2

    Rep:
    ooh i did t*gravity because i thought gravity = distance travelled down

    thanks : ) i forgot about the equations :/ Silly me.

    Rep:
    t*gravity =/= distance

    t*a (=t*g) would be the increase in speed (or the final speed in this case, as the initial vertical speed is 0). This can be seen just by looking at units:

    Units of (t*a) = Units of t * units of a = s * m/s^2 = m/s. This is a unit of velocity.

    TenOfThem (post 2) gives you the right equation to use.

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: October 28, 2011

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