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TOPIC: CALCULATION OF GRAVITATIONAL FORCE
Gravitational force:
This is the force with which the earth pulls all objects towards its centre. It is also called force of gravity. The instrument used for measuring gravitational force is called spring balance.
Calculation of gravitational forces:
The unit of force is Newton (the symbol is N). The unit was named after Sir Isaac Newton who first discovered the facts about gravity. The weight of a body is the force the earth exerts on it. All forces are measured in Newton. On the earth surface the universal value of acceleration due to gravity (g) is 9.8m/s2 or 10m/s2
To calculate gravitational force (Gf). The following formulae are used:
1.F=mg, used for calculation of gravitational force.
Example 1: Calculate the gravitational force required to pull down a mango fruit of 10kg falling with acceleration of 5m/s2.
Solution: F=mg, where F is unknown, m= 10kg, a= 5m/s2
:. F= 10 x 5 = 50 N.
Example 1: A mass of 300g is acted upon by a force which produces an acceleration of 5m/s2. Calculate the force.
Solution: F=mg,
Since mass is not given in kg, convert it to kg,
Mass = 300/1000= 0.3 kg
:. F= 0.3 x 5 = 1.5N
Example 2: Work done is defined as the product of force and the distance covered by the object.
Work done= force x distance
Wd=f x h where f=mg :. Wd= mgh
Work done= mgh used for calculation of work done against gravity, measured in joules. (J)
Where m = mass of the object measured in kilogram (Kg)
g = acceleration due to gravity measured in meter per seconds square (m|s2)
h = height of object measured in meter (m)
Example 3. What is the work done by a man who lifts a block of 30kg through a height of 3 meters? (g=10m/s2).
Solution
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