Final answer:
The power output by an 80-kg army trainee doing pull-ups can be calculated using the formula for power, which measures work done over time. Assuming the distance moved during a pull-up is 0.8 meters and using the force equal to the weight of the trainee multiplied by gravity, the power output is computed to be 784 watts.
Step-by-step explanation:
The question relates to the concept of power in physics, which is defined as the rate at which work is done. To calculate the power supplied by the trainee's muscles during the pull-ups, we can use the formula P = W/t, where P is power, W is work done, and t is the time taken. Given that the work done (W) is equal to the force applied (which is equal to the weight of the trainee) times the distance moved vertically, and assuming the average distance moved is about 0.8 meters (a reasonable estimate for the height of a pull-up), we can estimate the work done. The force applied by the trainee would be equivalent to the gravitational force, which is the product of the mass (80 kg) and the acceleration due to gravity (approximately 9.8 m/s2).
Hence, the force applied would be 80 kg × 9.8 m/s2 = 784 N. Therefore, the work done W = 784 N × 0.8 m = 627.2 J. Since the time taken for the pull-up is 0.8 seconds, the power output can be calculated as P = 627.2 J / 0.8 s = 784 W.