Question

10. Rank the following in terms of increasing power. A. Doing 100 J of work in 10 seconds. B. Doing 100 J of work in 5 seconds. C. Doing 200 J of work in 5 seconds. D. Doing 400 J of work in 30 seconds.

Answer 1

Answer:

In order from the lowest power

A. 10 W

D. 13.3 W

B. 20 W

D.40 W

Explanation:

The first step is to have all the measurements in watts or some similar units per time (like Horsepower). In this case using the standard International System is easier to work in watts.

So the formula, from Joules per second, to watts is:

$P(w)=E(j)/t(s)$

So,

A. $P(w)=E(j)/t(s)\\P(w)=100/10=10 w$

B. $P(w)=E(j)/t(s)\\P(w)=100/5=20 w$

C. $P(w)=E(j)/t(s)\\P(w)=200/5=40 w$

D. $P(w)=E(j)/t(s)\\P(w)=400/30=13.3 w$

And finally order according the previous condition: 10, 13.3. 20, 40.

Answer 2

A - 10 watts
D - 13-1/3 watts
B - 20 watts
C - 40 watts

Power = (work done) / (time to do it)