)what is the average useful power output of a person who does 6.00×106 j of useful work in 8.00 h? (b) working at this rate, how long will it take this person to lift 2000 kg of bricks 1.50 m to a platform? (work done to lift his body can be omitted because it is not considered useful output here.)

a) The average useful power output of a person is 208.3 W

b) It take 141.14 s for this person to lift 2000 kg of bricks 1.50 m to a platform

Explanation:

a) We know that,

Where ,

P is the power consumed  

W is the work done

t is the time elapsed

Given: t = 8 hr and  

Substituting known information in the power equation, we get

Convert hr into sec,

So,

b) Given:

m = 2000 kg

h = 1.50 m

we know,

The formula for potential energy depends on the force acting on the two objects. For the gravitational force the formula is , where m is the mass in kilograms, g is the acceleration due to gravity (at the surface of the earth) and h is the height in meters.

Put this in power equation, we get

From above, find time by substituting the known values, we get

good for her? ? where is the question?

the displacement produced by the body.  

the amount of force subjected to the body.  

the angle between the direction of force and displacement