A boy weighing 108-lb starts from rest at the bottom A of a 6-percent incline and increases his speed at a constant rate to 7 mi/hr as he passes B, 40 ft along the incline from A. Determine his power output as he approaches B.

Question

Engineering

Kenna

17 April, 23:03

A boy weighing 108-lb starts from rest at the bottom A of a 6-percent incline and increases his speed at a constant rate to 7 mi/hr as he passes B, 40 ft along the incline from A. Determine his power output as he approaches B.

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Answers (1)

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Cisco · Answer 1

88.18 W

Explanation:

The weight of the boy is given as 108 lb

Change to kg = 108*0.453592 = 48.988 kg = 49 kg

The slope is given as 6%, change it to degrees as

6/100 = 0.06

tan⁻ (0.06) = 3.43°

The boy is travelling at a constant speed up the slope = 7mi/hr

Change 7 mi/h to m/s

7*0.44704 = 3.13 m/s

Formula for power P=F*v where

P=power output

F=force

v=velocity

Finding force

F=m*g*sin 3.43°

F=49*9.81*sin 3.43° = 28.17

Finding the power out

P=28.17*3.13 = 88.18 W