Question

A ball rolls off the top of a stair way with a horizontal velocity of 4.5 m/s. If each step is 0.2 m high and 0.3 m broad, then the ball will strike the n^th step where n is equal to : (g = 10 m/s²)

• A. 3
• B. 4
• C. 6
• D. 9

Answer 1

Answer: (D)

9

Answer 2

As we have derived this formula in class room.

h = $\frac { 2 \mathrm { u } ^ { 2 } \mathrm {~h} } { \mathrm { gb } ^ { 2 } }$ = $\frac { 2 ( 4.5 ) ^ { 2 } \times 0.2 } { 10 ( 0.3 ) ^ { 2 } }$ = 9