An unruly demonstrator lifts a stone of mass 200gm from the ground and throws it at his opponent . At the time of projection , the stone is 150cm above the ground and has a speed 3.0m/sec.Calculate the work done by the demonstrator during the process . If it takes one second for the demonstrator to lift the stone and throw ,whar is the horsepower does he use?



Potential energy= m*g*h /m- mass/g- gravity/h- height/ PE= 200mg*9.8m/s/s*150h =2.94 j Kinetic energy =0.5*m*v^2 /m- mass / v - speed / =0.5*200mg*900m/s=9kj= 0.9j Total energy = PE + KE = 2.94 + 0.9 = 3.84 j HP = TE/ 746 = 5.14*10^ -3