1) A 2.40 kg ball is attached to a ceiling by a 1.40 m long string. The height of the room is 3 m. What is the gravitational potential energy of the ball relative to the ceiling?
2) A single barrel of oil contains the equivalent chemical PE of about 8 X 10^9 J. How high in the air could that much energy raise a million kilogram load, assuming it is all converted to gravitational PE? [Hint: Use the definition of PEG assuming g is constant.]
2) A single barrel of oil contains the equivalent chemical PE of about 8 X 10^9 J. How high in the air could that much energy raise a million kilogram load, assuming it is all converted to gravitational PE? [Hint: Use the definition of PEG assuming g is constant.]
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1) If you are measuring potential energy relative to the ceiling, then the ceiling has zero potential energy. Things above the ceiling have positive potential energy, and things below the ceiling have negative potential energy.
U = mgh = (2.4 kg)(9.8 m/s^2)(-1.4 m) = -32.9 J
2) You are given the energy must find the height. Very simple. Using the equation for gravitational potential energy, solve for the unknown h then plug in the values.
U = mgh
h = U / mg
h = (8 x 10^9 J) / (10^6 kg)(9.8 m/s^2)
h = 816 m
U = mgh = (2.4 kg)(9.8 m/s^2)(-1.4 m) = -32.9 J
2) You are given the energy must find the height. Very simple. Using the equation for gravitational potential energy, solve for the unknown h then plug in the values.
U = mgh
h = U / mg
h = (8 x 10^9 J) / (10^6 kg)(9.8 m/s^2)
h = 816 m