4. A projectile with a mass of 2.4 kg is fired from a cliff 125 m high with an initial velocity of 150 m/s, directed 41.0' above the horizontal. What are (a) the kinetic energy of the projectile just after firing and (b) its potential energy? (c) Use conservation of energy to find the speed of the projectile just before it strikes the ground. L. KEit PE; given : m = 1. ykg 4' ) KE : _ mv' (2.4 kg ) ( 150 m /)" : 17060 1 + 2940 J 8 - 41-0' KE = 27000 J = 11 940 J 9 : 4. 6 m /s' w. ) re . mgh (T . ME); . (T. MEOF :(2.4 kq ) (9-6 m/s' ) (125m) 24140) - 4 my PE : 2940J { (2 4 kg ) y' : 29440 J speed / v = 158 m/ 5. A 220-lb man jumps out a window into a fire net 36 ft below. The net stretches 4.4 it before bringing him to rest and tossing him back into the air. What is the potential energy of the stretched net if no energy is dissipated? 7. Two snow-covered peaks are at elevations of 862 m and 741 m above the valley between them. If a skier starts from rest on the higher peak and just coasted down without exerting any effort, at what speed would he arrive at the lower peak? ft. lb