Question

A ball rolls of the top of the stair way with a horizontal velocity u ms^–1. If the steps are h m high and b m wide, the ball will hit the edge of the nth step, if –

• A. n = $\frac{2hu}{gb^{2}}$
• B. n = $\frac{2hu^{2}}{gb^{2}}$
• C. n = $\frac{2hu^{2}}{gb}$
• D. n = $\frac{hu^{2}}{gb^{2}}$

Answer 1

Answer: (B)

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

Answer 2

Q R = u $\sqrt { \frac { 2 \mathrm { H } } { \mathrm { g } } }$ (horizontal projection)

nb = u $\sqrt { \frac { 2 \mathrm { nh } } { \mathrm { g } } }$ ̃ n = $\frac { 2 \mathrm { u } ^ { 2 } \mathrm {~h} } { \mathrm { gb } ^ { 2 } }$