Question

A weightlifter curls a 30 kg bar, raising it each time a distance of 0.50 m .How many times must he repeat this exercise to burn off the energy in one slice of pizza? Assume 25% efficiency. Energy content of one slice of pizza is 1260 kJ.

Answer 1

Answer:

$N = 2141 times$

Explanation:

Each time the work done to raise a given mass is

$W = mgh$

here we know that

$m = 30 kg$

$h = 0.50 m$

now we have

$W = (30 kg)(9.81 m/s^2)(0.50)$

$W = 147.15 J$

since it is just 25% of actual energy consumed as we know its efficiency is 25%

so we have total energy consumed in this way

$E_{total} = \frac{147.15}{0.25}$

$E_{total} = 588.6 J$

now if it took N number of times so burn the fat of a pizza then

$N(588.6) = 1260 \times 10^3$

$N = 2141 times$