A)
<img src="https://tex.z-dn.net/?f=E_p%3D%20m%2Ag%2Ah%3D%2018kg%2A9%2C8m%2Fs%5E2%2A25%2C5m%3D%204498%2C2%20joules" />
b) en el medio de la trayectoria,
h = 25, 5m / 2 = 12, 75m
la velocidad a esa altura es,
<img src="https://tex.z-dn.net/?f=v_f%5E2%3Dv_o%5E2-2g%28yf-yo%29%20%5C%5C%20v_f%3D%20%5Csqrt%7B-2g%2A%2812%2C75m-25%2C5m%29%7D%20%3D%20%5Csqrt%7B-2%2A9%2C8m%2Fs%5E2%2A%28-12%2C75m%29%7D%20%3D15%2C808m%2Fs%0A%0A" />
Por tanto la energia mecanica es,
<img src="https://tex.z-dn.net/?f=E_m%3DE_c%2BE_p%20%5C%5C%20%20%5Cfrac%7Bmv%5E2%7D%7B2%7D%20%2Bmgh%3D%20%5Cfrac%7B18kg%2A%2815%2C808m%2Fs%29%5E2%7D%7B2%7D%20%2B18kg%2A9%2C8m%2Fs%5E2%2A12%2C75m%3D%204498joules" />
C) la energia cinetica :
cuando toca el suelo la velocidad final es,
<img src="https://tex.z-dn.net/?f=v_f%5E2%3Dv_o%5E2-2g%28yf-yo%29%20%5C%5C%20v_f%3D%20%5Csqrt%7B-2g%2A%280-h%29%7D%20%3D%20%5Csqrt%7B-2%2A9%2C8m%2Fs%5E2%2A%28-25%2C5m%29%7D%20%3D22%2C35m%2Fs%20" />
<img src="https://tex.z-dn.net/?f=E_c%3D%5Cfrac%7Bmv%5E2%7D%7B2%7D%20%3D%5Cfrac%7B18kg%2A%2822%2C35m%2Fs%29%5E2%7D%7B2%7D%20%3D%204495joules" />.