AP Physics Green - Conserve Energy!

Remember everyone - energy is ONLY conserved if the only work is done by conservative forces. Check this EVERY time you use energy conservation to solve a problem.

Solutions:
36. v_f = 49.5 m/s

37. v_f = (2*g*H)^1/2 = 5.14 m/s

38. (1/2)m^v_o^2 + 0 = (1/2)m^v_f^2 + mgH

v_o = (v_f^2 + 2gH)^(1/2) = 6.45 m/s

40. In each case, you must derive that v_f = (2*g*(H - h2))^1/2

At B: v_f = (2*g*(30 m - 0 m))^1/2 = 24.2 m/s

At C: v_f = (2*g*(30 m - ? m))^1/2 = ANSWER PENDING

At D: v_f = (2*g*(30 m - 12 m))^1/2 = 18.8 m/s

41.
(1/2)m^v_o^2 + mgH = (1/2)m^v_f^2 + 0

v_f = (2gH + v₀^2)^(1/2) = 198.5 m/s.

You do NOT need to use the 45 degrees because v_o is the SPEED of the object at the top!