First slide

Work

Question

A body of mass 2 kg at rest acquires a velocity of 10ms^-1 in 4 seconds. The work done is

Moderate

A

$100 e r g s$
B

$10^{9} J$
C

$10^{9} ergs$
D

$1000J$

Solution

$\begin{array}{l} W = FScos θ = ma \frac{1}{2} {at}^{2} \cos θ \\ W = \frac{1}{2} m (\frac{v - u}{t}) [(\frac{v - u}{t}) \cdot t^{2}] \\ W = \frac{1}{2} \times 2 \times \frac{10}{4} \times \frac{10}{4} \times 16 \\ W = 100 J = 100 \times 10^{7} ergs \\ W = 10^{9} ergs \end{array}$

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