Question

A girl after being angry throws her engagement ring from the top of a building $12m$ high towards her boyfriend with an initial horizontal speed of $5m{s}^{-1}$, speed with which the ring it touches the ground is

• A. $5m{s}^{-1}$
• B. $14.3m{s}^{-1}$
• C. $1.5m{s}^{-1}$
• D. $16.2m{s}^{-1}$

Answer 1

The correct option is D $16.2m{s}^{-1}$

For motion along vertical direction $v_y^2=u_y^2+2gh=0+2\left(10\right)\left(12\right)=240$

As $v_x=5m/s$ so net velocity when it touches ground $=\sqrt{v_x^2+v_y^2}=\sqrt{25+240}=\sqrt{265}=16.2m/s$