A ball is thrown upwards from the ground with an initial velocity u. The ball is at a height of $80$ m at two times. The time interval being $6 s$ . Take $g = 10 m / s^{2}$ , the value of u is

100

m/s

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80

m/s

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50

m/s

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30

m/s

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Solution

The correct option is C $50$ m/s
From situation $B$ to $C$
$t = 6 s$
$⟹ \frac{2 v}{g} = 6$
$⟹ v = \frac{6 \times 10}{2} = 30 m / s$
Now from $A$ to $B$
$v^{2} = u^{2} + 2 a s$
$⟹ 30^{2} = u^{2} + 2 (- 10) (80)$
$⟹ u = 50 m / s$

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A ball is thrown upwards from the ground with an initial velocity u. The ball is at a height of 80m at two times. The time interval being 6s. Take g=10m/s2, the value of u is

The correct option is C 50m/sFrom situation B to Ct=6 s⟹2vg=6⟹v=6×102=30 m/sNow from A to Bv2=u2+2as⟹302=u2+2(−10)(80)⟹u=50 m/s

A ball is thrown upwards from the ground with an initial velocity u. The ball is at a height of $80$ m at two times. The time interval being $6 s$ . Take $g = 10 m / s^{2}$ , the value of u is

The correct option is C $50$ m/s
From situation $B$ to $C$
$t = 6 s$
$⟹ \frac{2 v}{g} = 6$
$⟹ v = \frac{6 \times 10}{2} = 30 m / s$
Now from $A$ to $B$
$v^{2} = u^{2} + 2 a s$
$⟹ 30^{2} = u^{2} + 2 (- 10) (80)$
$⟹ u = 50 m / s$