Homework Help: physics

Posted by sandhya on Tuesday, May 1, 2012 at 5:49am.

a ball rolls down a roof tht makes an angle of 30 to horizontal.it rolls off the egde with a speed of 5.00m/s.distance to the ground from that point is 7.00m
a)how long is the ball in the air
b)how far from the base of the house does it land?
c)what is its speed just before landing?

physics - Elena, Tuesday, May 1, 2012 at 8:09am
v(ox) = v•cosα =5•cos30 = 4.33 m/s,
v(x) = v(ox) = 4.33 m/s,
v(oy) = v•sinα =5•sin30 = 2.5m/s.
h =v(oy) •t+g•t^2/2,
4.9•t^2 +2.5•t-7 =0
t = 1.05 s.
L =v(ox) •t = 4.33•1.05 = 4.55 m
v(y) = v(oy) + g•t = 2.5 +9.8•1.05 = 12.8 m/s,
v=sqrt{v(x)^2 + v(y)^2} = 13.5 m/s.

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