Question

At the gym, a man pulls a bar on a machine that works the muscles of the upper back. It takes him 0. 5 seconds to raise 30

kilograms of weights a vertical distance of 0. 5 meters.


Which of these exerts the same power output? (Estimate g as 10 m/s2. )



A) lifting 25 kilograms a distance of 2. 4 meters in 2. 0 seconds



B) lifting 45 kilograms a distance of 2. 4 meters in 3. 0 seconds


C) leg pressing 45 kilograms a distance of 0. 5 meters in 0. 5 seconds.


D) bench pressing 30 ligrograms a distance of 0. 5 meter in 1. 5 seconds.


Pleaseeeeeee help me

Answer 1

The power output of the man pulling the bar can be calculated as follows:

Power = Work / Time

The work done by the man is equal to the force he exerts multiplied by the distance he moves the weights:

Work = Force x Distance

The force he exerts is equal to the weight of the weights he is lifting:

Force = Weight x g

where g is the acceleration due to gravity, which is approximately 10 m/s^2.

Plugging in the given values, we get:

Force = 30 kg x 10 m/s^2 = 300 N

Work = Force x Distance = 300 N x 0.5 m = 150 J

Power = Work / Time = 150 J / 0.5 s = 300 W

Now we can check which of the other options exerts the same power output:

Option A:

Force = 25 kg x 10 m/s^2 = 250 N

Work = Force x Distance = 250 N x 2.4 m = 600 J

Power = Work / Time = 600 J / 2.0 s = 300 W

Option B:

Force = 45 kg x 10 m/s^2 = 450 N

Work = Force x Distance = 450 N x 2.4 m = 1080 J

Power = Work / Time = 1080 J / 3.0 s = 360 W

Option C:

Force = 45 kg x 10 m/s^2 = 450 N

Work = Force x Distance = 450 N x 0.5 m = 225 J

Power = Work / Time = 225 J / 0.5 s = 450 W

Option D:

Force = 30 kg x 10 m/s^2 = 300 N

Work = Force x Distance = 300 N x 0.5 m = 150 J

Power = Work / Time = 150 J / 1.5 s = 100 W

Therefore, options A and B exert the same power output as the man pulling the bar, while options C and D do not.