Question

The acceleration due to gravity at a place is \({g = 9.61\, m \, s^{-2}}). The speed with which a ball must be thrown vertically upward from the ground level so that it reached a maximum height of 50 m is

• A. \({28\, m \, s^{-2}})
• B. \({30\, m \, s^{-2}})
• C. \({31\, m \, s^{-2}})
• D. \({29\, m \, s^{-2}})

Answer 1

Answer: (C)

${31\, m \, s^{-2}}$

Answer 2

Given $h$ = 50 m
$a$ = - g = -9.8 m s$^{-2}$ and $v$ = 0
For vertically upward motion
$v^2 = u^2 - 2gh$
${u = \sqrt{2gh} = \sqrt{19.6 \times 50} = 31.30 \, m s^{-1}}$