Question

Mary takes 6.0 seconds to run up a flight of stairs that is 102 meters long. if mary's weight is 87 newtons, what power has mary exerted?

Answer 1

Thank you for posting your question here at brainly. I hope the answer will help. Below are the choices that can be found elsewhere:

 A. 1.5 * 10^3 Watts 
B. 7.3 * 10^2 Watts 
C. 3.5 * 10^2 Watts 
D. 2.5 * 10^2 Watts

 Work = force*displacement = 10^2*87 = 8,700 joule 
Power = work/time = 8,700/6 = 1.45*10^3 (rounded up to 1.5 kw). The answer is A. 

Answer 2

Answer: 1479 W

Explanation:

The work done by Mary is equal to its gain in gravitational potential energy, which is equal to

$W=\Delta U=mg\Delta h$

where

$mg=87 N$ is Mary's weight

$\Delta h=102 m$ is the distance

Substituting,

$W=(mg)(d)=(87 N)(102 m)=8,874 J$

And the power is equal to the ratio between the work done and the time taken:

$P=\frac{W}{t}=\frac{8,874 J}{6.0 s}=1479 W=1.48 kW$