Figure 4.3
Note that, work has the units of force (N) and distance (m). Therefore its unit is newton - metre, but this unit has a special name: Joule (J).
1 N * 1 m = 1 N * m = 1 J.
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A larger unit of work is the kilojoule. 1 kJ = 1 000 J.
A common unit of energy is called the calorie.
1 calorie (cal) is equal to 4.18 joules (J). 1 cal = 4.18 J
Energy.
What is Energy?
If an object has energy it can do work, so we can define energy as the ability to do work. We do work by using energy, so we can say that work and energy should have the same units. Both work and energy are measured in joules (J).
For instance, in Figure 4.5 the work done of the object is, W=50N*4 m =200J.
How much energy is spent? Since the energy spend is equal to the work done, the answer is: 200 J
Look at Table 4.1 and state how much energy we spent in the listed activities.
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