Question

The human brain consumes about 21.3 W of power under normal conditions. (More power may be required during exams...) How long can a candy bar (299 Calories) power the normally functioning brain? Note: The nutritional Calorie is equivalent to 1000 calories, or 1 kcal, as defined in physics; 1 kcal = 4186 J.

How fast must you lift a 3.60 kg container of milk if the power output of your arm is to be 21.3 W?

Answer 1

i used the eqn P=W/T and i did some unit conversions to get the 299 calories into Joules but the answer is wrong...

Answer 2

A candy bar has 299,000 (gram)-calories or 1.252*10^6 J.
Set 21.3 J/s * T = 1.252*10^6 J
and solve for the time T, in seconds