Solve the following :


An unruly demonstrator lifts a stone of mass $200 \mathrm{~g}$ from the ground and throws it at his opponent. At the time of projection, the stone is $150 \mathrm{~cm}$ above the ground and has a speed of $3.00 \mathrm{~m} / \mathrm{s}$. Calculate the work done by the demonstrator during the process. If it takes one second for the demonstrator to lift the stone and throw, what horsepower does he use?


Work done $\mathrm{W}=\mathrm{mgh}+^{\frac{1}{2}} \mathrm{mv}^{2}$

$W=0.2 \times 9.8 \times 1.5+\left({ }^{\frac{1}{2}} \times 0.2 \times 3^{2}\right)$

$W=3.84 \mathrm{~J}$

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