A baseball of mass 0.25 kg is thrown in the air with an initial speed of 30m/s but because of air resistance, the ball returns to the ground with a speed of 27m/s. Find the work done by air resistance.
Correct answer: A. -21.37J
- A. -21.37J
- B. 15 J
- C. 21.37 J
- D. -15 J
Explanation
The work done by air resistance can be determined by the change in kinetic energy of the baseball. The initial kinetic energy (KEinitial) is given by:KEinitial = 0.5 × 0.25 kg × (30 m/s)2 = 112.5 JThe final kinetic energy (KEfinal) when it returns to the ground is:KEfinal = 0.5 × 0.25 kg × (27 m/s)2 = 91.125 JThe work done by air resistance is the difference in kinetic energy: Work = KEfinal - KEinitial = 91.125 J - 112.5 J = -21.375 JTherefore, Option A is correct. Other options either have incorrect values or do not account for the negative sign, indicating energy loss due to air resistance.
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