A man throws a ball vertically upward and it rises through 20 m and returns to his hands. What was i

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2.Motion in Straight Line

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A man throws a ball vertically upward and it rises through $20 \;m$ and returns to his hands. What was the initial velocity $(u)$ of the ball and for how much time $(T)$ it remained in the air $[g = 10\,m/{s^2}]$

A

$u = 10\, m/s, T = 2s$

B

$u = 10\, m/s, T = 4s$

C

$u = 20 \,m/s, T = 2s$

D

$u = 20 \,m/s, T = 4s$

Solution

(d) $u = \sqrt {2gh} = \sqrt {2 \times 10 \times 20} = 20\;m/s$

and $T = \frac{{2u}}{g} = \frac{{2 \times 20}}{{10}} = 4\,sec$

Standard 11

Physics

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