Question

A small body of mass $100gm$ is thrown horizontally from top of a high tower with initial speed $9m/s$. The power delivered (in watt) by force of gravity when its velocity is making an angle of ${45}^{\circ }$ with vertical is $x\sqrt{2}$. Find $x$.
($g=10m/s^2$)

Answer 1

$45^{0}anglemeans\frac{v_y}{v_x}=1,i.e.\frac{0+10t}{9}=1ort=0.9secondsThus,vecv=9\hat{i}-9\hat{j}orspeed=9\sqrt{2}m/sThusP=Force\times speed=9\sqrt{2}mg=9\sqrt{2}\times 0.1\times 10=9\sqrt{2}NThusx=9$