Question 12
Work, Energy and PowerAn object of mass 100 g projected vertically upwards from the ground level has a velocity of 20 m s−1 at a height of 10 m. Calculate its initial kinetic energy at the ground level. [g = 10 m s−2, neglect air resistance]
- A.10 J
- B.20 J
- C.30 J
- D.50 J
Show the answer and explanation
Answer: C (30 J)
Explanation
Energy is conserved. At 10 m: KE = ½ × 0.1 × 202 = 20 J and PE = 0.1 × 10 × 10 = 10 J. The initial KE was 20 + 10 = 30 J.