Question

A staircase contains three steps each 10 cm high and 20 cm wide. What should be the minimum horizontal velocity of a ball rolling off the uppermost plane so as to hit directly the lowest plane

• A. 0.5 m/s
• B. 1 m/s
• C. 2 m/s
• D. 4 m/s

Answer 1

Answer: (C)

2 m/s

Answer 2

Formula for this condition is given by $n = \frac{2hu^{2}}{gb^{2}}$

⇒$3 = \frac{2 \times 10 \times u^{2}}{10 \times 20^{2}} \Rightarrow u^{2} = 200cm/sec = 2m/sec$

where h = height of each step, b = width of step, u = horizontal velocity of projection, n = number of step.