A ball rolls off the top of a staircase with velocity u m/s . If the steps are h metre high and b metre wide, the ball will hit the edge of nth step, when
A
n=2hugb2
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B
n=2hu2gb
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C
n=2hu2gb2
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D
n=hu2gb2
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Solution
The correct option is Cn=2hu2gb2 If the ball hits the nth step, then vertical distance travelled = nh. Here, velocity along horizontal direction = u and distance travelled in horizontal direction is nb = ut. ⇒t=nbu
. Initial velocity in vertical direction is 0 and distance travelled in vertical direction will be given by nh=gt22 .Putting value of t in above equation ,we get nh=g2(nbu)2⇒n=2hu2gb2