Final answer:
The total work done by the football player when completing 20 pull-ups, with each pull-up lifting him 0.2 meters, is 1176 Joules.
Step-by-step explanation:
The student asked about the total work done by the football player who has a mass of 30 kg when doing 20 pull-ups and lifting himself a distance of 0.2 meters each time. Work is defined in physics as the product of force and displacement in the direction of the force. Since the force required during a pull-up is equal to the weight of the football player (force of gravity on the player), we calculate it using the equation:
Work (W) = Force (F) × Displacement (s)
Therefore, the force exerted by the player equals his weight, which is calculated by multiplying the mass (m) by the acceleration due to gravity (g, approximately 9.8 m/s2). Thus:
F = m × g = 30 kg × 9.8 m/s2 = 294 N (Newton)
We calculate the work done for one pull-up and multiply it by the number of pull-ups (20):
W = F × s = 294 N × 0.2 m = 58.8 J (Joules) per pull-up
Total work for 20 pull-ups: Wtotal = 58.8 J × 20 = 1176 J