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New Zealand
Level 6 - NCEA Level 1

Energy in the body

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.


$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.


Convert $3108$3108 kilojoules into kilocalories, using $1$1 kilocalorie$=$=$4.2$4.2 kilojoules.


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$1835 inactive $8000$8000 $10500$10500
  active $9000$9000 $12500$12500
  very active $10500$10500 $14800$14800
$36-70$3670 inactive $8000$8000 $10000$10000
  active $8800$8800 $11800$11800
  very active $10400$10400 $14300$14300











Apply the relationships between units in the metric system, including the units for measuring different attributes and derived measures


Apply measurement in solving problems

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