Question

The height and width of each step of a staircase are 20cm and 30cm respectively. A ball rolls off the top of a stair with horizontal velocity v and hits the fifth step. The magnitude of v is?

• A. 22.42
• B. 43.23
• C. 12.12
• D. 33.54

Answer 1

The correct option is D 33.54

$s=ut+\frac{1}{2}a{t}^2$

$5\times 20=0+\frac{1}{2}\times 10\times {\left(\frac{5\times 30}{u}\right)}^2$

$100=5\times {\left(\frac{150}{u}\right)}^2$

$u^2=1125$

$\Rightarrow u=33.54$