A person holding a dog of mass 9.9 kg starts walking in a straight line for 5 m
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A person holding a dog of mass 9.9 kg starts walking in a straight line for 5 m

[From: ] [author: ] [Date: 12-06-21] [Hit: ]
2 s = 15.18 J/s = 15.......
A person holding a dog of mass 9.9 kg starts walking in a straight line for 5 m, then they walk up some stairs which have a length (not height) of 3 m and are placed at an angle 22° to the horizontal.

The total amount of work done by the person on the dog is:

What is the total power expended on the dog if the person walks at a constant speed of 0.85 m/s?

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Assuming the dog is not lifted or lowered, 0 Work in the 5 m of horizontal motion.

We need how high the dog was moved vertically.

Hypotenuse = 3 m

sin 22 = Y/3
Y = 1.12 m

Now the dog's change in Potential Energy

PE = MGH = 9.9 kg * 9.8 m/s^2 * 1.12 m = 109.03 Joules = Work

The person walked 5 + 1,12 = 6.12 m

distance = velocity * time

6.12 = 0.85 m/s * t

t = 7.2 s

Power = Energy/ time = 109.3 J / 7.2 s = 15.18 J/s = 15.18 Watt
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