Problems ? Potential Energy vs. Kinetic Energy P4-4. An athlete bench-presses 14

Question

Problems ? Potential Energy vs. Kinetic Energy P4-4. An athlete bench-presses 140 kg a vertical distance of 30 cm. Find the weight's change in GPE. P4-5.. Meteoroids often move at high speeds relative to the Earth. If meteoroids approach Earth closely enough to hit our atmosphere, friction heats them and they radiate, causing a spectacular light display. If a 15 gram (about marble-sized) meteoroid approaches at 50 km/s, A) find the meteoroid's kinetic energy. B) How fast would a 1900 kg auto have to move to achieve the same KE?

Explanation / Answer

change in GPE = mgh = 140*9.8*0.3 = 411.6 J
4-5
A)
kinetic energy =0.5mv^2 = 0.5*0.015*50^2*10^6 =18.75x10^6 J
B)
0.5Mv1^2 = 18.75*10^6
V1 = 163.66 m/s

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