An 80 kg man climbs a 50 m-high hill in 20 minutes. What is the average power in watts he expends climbing the hill?
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To calculate the average power in watts, we can use the formula:
Power = Work / Time
To find the work done, we can use the formula:
Work = Force × Distance
In this case, the force exerted is equal to the weight, which is the mass multiplied by the acceleration due to gravity (9.8 m/s²). The distance is given as 50 m. The time is given as 20 minutes, but we need to convert it to seconds.
To convert minutes to seconds, we multiply by 60:
20 minutes × 60 seconds/minute = 1200 seconds
Now, let's calculate the work:
Work = (80 kg × 9.8 m/s²) × 50 m
Work = 39,200 joules
Finally, divide the work by the time:
Power = 39,200 joules / 1200 seconds
Power ≈ 32.66 watts
Therefore, the average power expended by the man climbing the hill is approximately 32.66 watts.