A ball of mass 0.10 kg is located 1.81 m above the surface of the ground. It is
ID: 1752524 • Letter: A
Question
A ball of mass 0.10 kg is located 1.81m above the surface of the ground. It is released fromrest, falls straight down, and hits the ground. How much work wasdone by the force of gravity?What is the speed of the ball just before it hits the ground?Neglect the effect of air friction.
What height would the ball have to bereleased from in order to reach a speed of 14.30m/s (i.e., 32.00 mi/hr) justbefore hitting the ground?
A ball of mass 0.10 kg is located 1.81m above the surface of the ground. It is released fromrest, falls straight down, and hits the ground. How much work wasdone by the force of gravity?
What is the speed of the ball just before it hits the ground?Neglect the effect of air friction.
Explanation / Answer
For a vertical displacement y, the work done by gravity is W = -m gy, so W = -.10 kg * g * -1.81 m = .000181 m kg^2 The speed of the ball is given by conservation of energy; original energy is given by m g h. This is all converted to kinetic energy, of the form 1/2 m v^2. So 1/2 m v^2 = m g h, and so v=(2 g h)= 5.958 m/s This would give v=14.30 m/s = (2 g h), so h = (14.30 m/s)^2/ (2 g) = 102245 m
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