Chapter 4, Problem 1RP

If 100 W of power occurs for 30 s, how much energy, in joules, is used?

To determine

Calculate the energy in joules.

Answer to Problem 1RP

The energy in joules is $\underset{\_}{3000\text{J}}$.

Explanation of Solution

Calculation:

Write the general expression to find the energy.

$W=Pt$        (1)

Here,

P is the power, and

t is the time.

Substitute $100\text{W}$ for P and 30 s for t in equation (1) to find the energy in joules.

$\begin{array}{c}W=\left(100\text{W}\right)\left(300\text{s}\right)\\ =3000\text{W}\cdot \text{s}\\ =3000\text{J }\left\{\because \text{1}\text{J}=1\text{W}\cdot 1\text{s}\right\}\end{array}$

Conclusion:

Thus, the energy in joules is $\underset{\_}{3000\text{J}}$.