A body accelerates uniformly from rest to a velocity of $1 m s^{- 1}$ in 15 second. In what time the kinetic energy of the body will be $\frac{2}{9} J$ .[Take mass of body as 1kg]:

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Solution

The correct option is C 10s
given, $v = 1 m / s, t_{1} = 15 s, K . E = \frac{2}{9} J, t_{2} = ?$
As, $v = u + a t_{1}$
$a = \frac{1 - 0}{15} m s^{- 2}$ $= \frac{1}{15} m s^{- 2}$
Also, $K . E = \frac{1}{2} \times 1 \times v^{2} = \frac{2}{9} J$
or $v = \frac{2}{3} m s^{- 1}$
Now, $\frac{2}{3} = 0 + \frac{1}{15} \times t_{2}$
or $t_{2} = 10 s$

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A body accelerates uniformly from rest to a velocity of 1ms−1 in 15 second. In what time the kinetic energy of the body will be 29J.[Take mass of body as 1kg]:

The correct option is C 10sgiven,v=1m/s,t1=15s,K.E=29J,t2=?As,v=u+at1a=1−015ms−2=115ms−2Also,K.E=12×1×v2=29Jor v=23ms−1Now,23=0+115×t2 or t2=10s

A body accelerates uniformly from rest to a velocity of $1 m s^{- 1}$ in 15 second. In what time the kinetic energy of the body will be $\frac{2}{9} J$ .[Take mass of body as 1kg]: