Question

A body dropped from a height $h$ with an initial speed zero, strikes the ground with a velocity$3km/h$. Another body of same mass is dropped from the same height $h$ with an initial speed $- u^{'} = 4km/h$ . Find the final velocity of second body with which it strikes the ground

• A. 3 km/h
• B. 4 km/h
• C. 5 km/h
• D. 12 km/h

Answer 1

Answer: (C)

5 km/h

Answer 2

For first case $v^{2} - 0^{2} = 2gh$

⇒ $(3)^{2} = 2gh$

For second case $v^{2} = ( - u)^{2} + 2gh = 4^{2} + 3^{2}\therefore v =$5km/h