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Homework Help: Projectile Question!

  1. Oct 31, 2005 #1
    A ball rolls horizontally off the top of a stairway with a speed of 1.52m/s. The steps are 1.52 cm high, and 20.3 cm wide, which step does the ball hit first.

    I dont really know where to start, I kept trying to use the formulas..but I would always end up with two unknowns.

    Can anyone point me in the right direction?
  2. jcsd
  3. Oct 31, 2005 #2
    The range of the ball is vT, where v = 1.52m/s and T is the duration: T = ROOT(2gnh)/g where h is the height of a step and n is the number of them passed. The range is also the sum of the widths of the steps passed, so:

    nw = v/g x ROOT(2gnh)

    where w = 20.3 x 10^-2.

    Rearrange and solve for n, rounding down.
  4. Nov 1, 2005 #3
    Sorry, I was counting steps 'across' when I said round down. You should round up for how many steps down the ball goes. Makes more sense.
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