  Question

With what speed a body be thrown upwards so that the distance traversed in $${5}^{th}$$ second and $${6}^{th}$$ seconds are equal?

A
5.84 m/s  B
49 m/s  C
98 m/s  D
98 m/s  Solution

The correct option is B $$49\ m/s$$Given,A body is thrown upward at speed, uAt 5th and 6th distance travel is equal = $$s$$ Mean in 4sec to 5 sec distance travel = $$s$$And in 5sec to 6 sec distance travel = $$s$$ It is only possible if body deaccelerated in 4sec to 5 sec and accelerated in 5sec to 6 secIn projectile motion, this condition is suited, if in 4sec to 5 sec body go upward, and in 5sec to 6 sec body go downward. So, at 5sec body is at top, and its vertical velocity is zero.Acceleration of gravity, $$g$$ Time, $$t$$ Initial velocity, $$u$$Final velocity, $$v$$ Apply kinematic equation at top position.$$v=u-gt$$$$0=u-gt$$ $$u=gt=9.81\times 5=49.01\,\,m/s$$ Hence, body thrown upward at speed $$49\,\,m/s$$ Physics

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