Page 68 - Physics

Physics for Secondary Schools

It should be understood that, the weight of an force of gravity is 10 newtons per kilogram
object is related to its mass. For instance, on (10 N/kg).
the earth’s surface, an object with a weight Note that, the acceleration due to gravity
of 1 N has also a mass of approximately varies depending on the reference body. For
0.1 kg or 100 g. The ratio of weight (N)
to mass (kg) gives approximately 10 N/kg example, the acceleration due to gravity
which is always constant and is represented on the moon g is equal to one-sixth of the
m
by “g”. acceleration due to gravity on the earth, g .
e
1
So, g has two meanings: That is, g = 6 × g e
m
1. It is the gravitational fi eld strength If g = 10 N/kg ,
of the earth (10 N/kg); and e
1
2. It is the acceleration due to gravity then, g = × 10 N/kg = 1.67 N/kg⋅
m
(10 m/s ). 6
2
Near the earth’s surface, there is a force of Thus, you would weigh less on the moon
gravity of 10 newtons for each kilogram than on the earth, even though your mass
of mass (see Figure 3.5). Thus, the earth’s remains constant.

m
60 kg
1 kg

10 N mg
600 N

Figure 3.5: Force of gravity acting on the bodies

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Student’s Book Form One

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