Physical Science math equation question

Question

A 

170.0 lb

 student runs up a stairway to a classroom 

21.5 ft

 above ground level in 

10.0 s.

 

(a) How much work did the student do?

 

 ft

·

lb

 

(b) What was the average power output in hp?

 

 hp

Answer 1

A) Definition of Work - amount of energy spent by an external force to displace an object. Note, the work can be done over a short period of time or may take longer. Time does not matter. The generic definition of work is

W = F x d

where, F is the external force and d is the displacement of the object.

In this case, the 'object' is the student with a mass of 170lbs. He 'works' against gravity to climb the stairs and raise himself 21.5ft above the ground. You can assume g = 32.17 ft/s²

B) Definition of Power - Power is the amount of energy spent per unit time. In other words, power is a measure of how fast the work is performed (i.e. energy is spent).

P = W/t

Now you should be able to perform the calculations. Horsepower (HP) is a unit in the FPS (Foot-Pound-Second) or English system. Since all the units above in the same system, your answer will be in HP.