Page 58 - 05. Subyek Teknik Mesin - Automobile Mechanical and Electrical Systems Automotive Technology Vehicle Maintenance and Repair (Vehicle Maintenance Repr Nv2) by Tom Denton

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Figure 1.58 Mass on the Earth and Moon remains the same but the weight will change

1.4.10 Mass, weight and force

Mass is the quantity of matter in a body as measured by its resistance to
Key fact
movement. The SI system base unit of mass is the kilogram (kg). The mass
of an object such as a car determines how much driving force is needed to The mass of an object determines
produce acceleration. The mass also determines the force exerted on a body how much driving force is needed to
produce acceleration.
by gravity.
The force F , mass m and acceleration a (or g , if due to gravity) can be calculated
using:

Force Mass Acceleration
F ma

Or
(
Force weight) Mass Gravity

F mg
At a given place, equal masses experience equal gravity, which are known as the
weights of the bodies. Masses can be compared by comparing the weights of
bodies as long as they are at the same place ( Fig. 1.58 ).

1.4.11 Volume and density

Density is a measure of the compactness of a substance; it is measured in
3
3
kilograms per cubic metre (kg/m or kg m . The density D of a mass m ,
occupying a volume V , is given by:
Density Mass/Volume Defi nition
D m V/ Relative density
Relative density is the ratio of the density of one substance to another. This The ratio of the density of one
is useful for testing older types of battery by comparing the density of the substance to another.
electrolyte to that of water ( Fig. 1.59 ). It is sometimes described as specifi c
gravity.