Question

How fast would a 130kg person have to run in (m/s) in order to have the same energy as that of a 100 W light bulb uses per hour.

Answer 1

Answer:

74.4 m/s

Explanation:

The power of the light bulb is

P = 100 W

We can find the energy used by the light bulb in one hour by using the equation

$E=Pt$

where

t = 1 h = 3600 s is the time interval

Substituting,

$E=(100)(3600)=360,000 J$

Now, we want the person to have the same energy. Since he is running, we are talking about kinetic energy, which is given by

$K=\frac{1}{2}mv^2$ (1)

where

m = 130 kg is the mass of the person

v is his speed

We said that his kinetic energy must be equal to the energy used by the bulb:

K = 360,000 J

Therefore, we can rearrange eq.(1) to find what speed the man should have:

$v=\sqrt{\frac{2K}{m}}=\sqrt{\frac{2(360,000)}{130}}=74.4 m/s$