Chapter 21, Problem 95A

(a)

Interpretation Introduction

Interpretation: The given unit in Joules needs to be converted into kilojoules.

Concept Introduction: A measurement in one set of units can be converted into another set of units using a conversion factor.

Explanation of Solution

The unit conversion factor used in this case will be:

  $\frac{1000\text{ J}}{1\text{ kJ}}$

Now, the given value is $4.32\times {10}^5\text{ J}$ .

The value in KJ can be calculated as follows:

  $\begin{array}{c}x=4.32\times {10}^5\text{ J}\left(\frac{1\text{ kJ}}{1000\text{ J}}\right)\\ =432\text{ kJ}\end{array}$

Thus, the correct converted value is 432 kJ.

(b)

Interpretation Introduction

Interpretation: The given unit in Calories needs to be converted to calories.

Concept Introduction: A measurement in one set of units can be converted into another set of units using a conversion factor.

Explanation of Solution

The unit conversion factor used in this case will be:

  $\frac{1000\text{ calories}}{1\text{ Calories}}$

Now, the given value is 255 Calories.

The value in calories can be calculated as follows:

  $\begin{array}{c}x=255\text{ Calories}\left(\frac{1000\text{ calories}}{1\text{ Calories}}\right)\\ =2.55\times {10}^5\text{ calories}\end{array}$

Thus, the correct converted value is $2.55\times {10}^5\text{ calories}$ .

(c)

Interpretation Introduction

Interpretation: The given value in calories needs to be converted into Joules.

Concept Introduction: A measurement in one set of units can be converted into another set of units using a conversion factor.

Explanation of Solution

The unit conversion factor used in this case will be:

  $\frac{4.2\text{ J}}{1\text{ calories}}$

Now, the given value is 645 calories.

The unit can be concerned into Joules as follows:

  $\begin{array}{c}x=645\text{ calories}\left(\frac{4.2\text{ J}}{1\text{ calories}}\right)\\ =2708\text{ J}\end{array}$

Thus, the correct converted value is $2708\text{ J}$ .