Q50 - Work, energy and power

The correct answer is A) 1000 J.

First, convert the speed to SI units: divide km/h by 3.6.

36 km/h ÷ 3.6 = 10 m/s

Then apply the kinetic energy formula:

KE = ½ m v² = ½ × 20 × 10² = ½ × 20 × 100 = 1000 J

Common traps: forgetting the ½ gives 2000 J (E); multiplying mass by speed gives 200 (D), which is momentum, not energy; using 36 without converting gives numbers that are not among the options.