Question

A ball rolls off top of a staircase with a horizontal velocity um/s. If the steps are h metre high and bmere wide, the ball will just hit the edge of nth step if n equals to

• A. $\frac{hu^{2}}{gb^{2}}$
• B. $\frac{u^{2}8}{gb^{2}}$
• C. $\frac{2hu^{2}}{gb^{2}}$
• D. $\frac{2u^{2}g}{hb^{2}}$

Answer 1

Answer: (C)

$\frac{2hu^{2}}{gb^{2}}$

Answer 2

By using equation of trajectory $y = \frac{gx^{2}}{2u^{2}}$ for given condition

$nh = \frac{g(nb)^{2}}{2u^{2}}$ $\therefore n = \frac{2hu^{2}}{gb^{2}}$