A body with a mass of 5 kg has the same kinetic energy as a second body. The second body has a mass of 10 kg and is moving at a speed of 20 m/s. How fast is the first body moving?
Answer (2)
First body:
E k 1 = 2 1 . m . v 2 E k 1 = 2 1 .5. v 1 2 = 2 5 . v 1 2
Second body:
E k 2 = 2 1 . m . v 2 2 E k 2 = 2 1 .10. ( 20 ) 2 = 2.000 J
From description of the task we have:
E k 1 = E k 2 2 5 . v 1 2 = 2.000 J 5. v 1 2 = 4.000 J v 1 2 = 800 J v 1 = 800 J ≈ 28 , 3 m / s
The speed of the first body, which has a mass of 5 kg, is approximately 28.3 m/s. This is derived from equalizing its kinetic energy with that of the second body, which has a mass of 10 kg and is moving at 20 m/s. Using the kinetic energy formula, we calculated the necessary values step by step.
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