A 1.4kg falling object (subject to the effects of aerodynamicdrag) is 1800m high
ID: 2262233 • Letter: A
Question
A 1.4kg falling object (subject to the effects of aerodynamicdrag) is 1800m high, traveling at 34 m/s and has not yet reached terminal speed. It first reaches terminal speed at a heightof 1340 m and the terminal speed is 37.3 m/s. a) How much thermal (internal) energy is generated through theaction of the drag force as the object falls from 1800m to1340m? b) Repeat a for the fall between 1340m and 500m. All solutions must be based on work and/or energymethods. A 1.4kg falling object (subject to the effects of aerodynamicdrag) is 1800m high, traveling at 34 m/s and has not yet reached terminal speed. It first reaches terminal speed at a heightof 1340 m and the terminal speed is 37.3 m/s. a) How much thermal (internal) energy is generated through theaction of the drag force as the object falls from 1800m to1340m? b) Repeat a for the fall between 1340m and 500m. All solutions must be based on work and/or energymethods.Explanation / Answer
a)
work done by friction + workdone by gravity = change in kinetic energy
Wg + Wf = 0.5*m*(v2^2-v1^2)
1.4*9.8*(1800-1340) + Wf = 0.5*1.4*(37.3^2-34^2)
6311.2 + Wf = 164.703
Wf = -6146.497 J
work done by friction = thermal energy generated = 6146.497 J
b)
work done by friction + workdone by gravity = change in kinetic energy
Wg + Wf = 0.5*m*(v2^2-v1^2)
1.4*9.8*(1340-500) + Wf = 0 (since velocity is not chinging)
Wf = -11524.8 J
work done by friction = thermal energy generated = 11524.8 J
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