Measurement
New Zealand
Level 6 - NCEA Level 1
Energy in the body
Lesson
We normally think of calories as being something to avoid. However, a calorie is simply a measurement of energy. Too many calories can be bad for your health as any unused energy is stored in the body as fat. Without any energy though your body wouldn't be able to function. Think about your smartphone, it's not much use to you when it doesn't have any energy! Also keep in mind when you buy an energy drink, you could also be thinking about it as a calorie drink! Probably doesn't seem as appealing now, does it?
Just like we can measure length in lots of different ways (inches, centimetres and so forth) there are different ways to measure the amount of energy in food. Two of the most common ways to measure energy are in calories or in kilojoules.
Remember!
$1$1 calorie is approximately $4.2$4.2 kilojoules
Worked Examples
Question 1
Convert $25$25 kilocalories into kilojoules, using $1$1 kilocalorie$=$=$4.2$4.2 kilojoules.
QUESTION 2
Convert $3108$3108 kilojoules into kilocalories, using $1$1 kilocalorie$=$=$4.2$4.2 kilojoules.
QUESTION 3
According to the table, how many kilojoules would a very active female in her 60's require per day?
| Age | Activity Level | Women (kJ/day) | Men (kJ/day) |
|---|---|---|---|
| $18-35$18−35 | inactive | $8000$8000 | $10500$10500 |
| active | $9000$9000 | $12500$12500 | |
| very active | $10500$10500 | $14800$14800 | |
| $36-70$36−70 | inactive | $8000$8000 | $10000$10000 |
| active | $8800$8800 | $11800$11800 | |
| very active | $10400$10400 | $14300$14300 |