FORM 1-PHYSICS-FORCE

FORCE
A force is an interaction that causes a change. In mechanics, a force is an interaction that causes a change in velocity (an interaction that causes acceleration).
Fundamental Types of Forces
Identify fundamental types of forces
There are two main types of forces namely:
  1. Fundamental forces
  2. Non fundamental forces
Fundamental Forces
Fundamental forces are the basic forces in nature that cannot be explained by the action of another force.
There are four types of fundamental forces. These include:
  1. The force of gravity
  2. The electromagnetic force
  3. The strong nuclear force
  4. The weak nucleus force
Force of gravity (weight)
The force of gravity is the pull by which the earth, moon and other very large bodies attract other objects towards themselves. It is commonly referred to as the weight of the object that is attracted.
All objects on the earth experience a force of gravity that is directed downwards towards centre of the earth. The earth’s gravitational pull is so great that it is able to hold most things firmly on the ground.
In mechanics, a freely falling body in the air moves down irrespective of its mass. This is due to force of gravity.
Example 1
A fruit fall from a tree because the earth exerts gravitational force on it. The force of gravity on the earth is always equal to the weight of the object (body).
Force of gravity, W = mass (m) x gravitational acceleration (g).
W= mg
Where acceleration due to gravity on the earth, g = 9.8m/s2
Conclusion, we can say that the force of gravity has the following properties.
  1. It pulls (attracts) objects towards the centre of the earth.
  2. It is directly proportional to the mass of the object. This means that the greater the mass the greater the pull of gravity.
  3. It is strong when the mass is closer to the centre of the earth.
NB: It should be noted that the weight of an object is directly related to its Mass.
Weight, W = mass x g = mg
The g above has two meanings:
  1. It is the gravitation’s field strength (10N/Kg)
  2. It is the acceleration of free fall (10m/s2
Electromagnetic force
This force includes both electric and magnetic force. It is relatively strong.
Example 2
Examples where electromagnetic forces are involved include:
  1. In the formation of molecules of a substance. Atoms attract each other to form molecules. This is due to electromagnetic force.
  2. In two parallel wires carrying current. If places near each other, the electromagnetic force acts on the wires.
Strong nuclear force
This is the force, which holds of the constitutions (sub atomic particles) of the atomic nucleus. It acts within the nucleus of the atom.
Weak nuclear force
This is the force which appears only in certain nuclear processes.
The Properties of Each Type of Fundamental Forces
Describe the properties of each type of the fundamental forces
Properties of gravitational forces
The following are the properties of gravitational force
  • It always attracts objects.
  • It is the weakest force among the four basic forces.
  • It is a central force (gravitational force between two objects acts along the line joining the centres of the objects.
  • It operates over very long distance.
Properties of electromagnetic force include
  • It may be attractive or repulsive is nature
  • It is a central force
  • It is stronger than gravitational force
  • It is also a long-range force (operates over a very long distance)
Properties of a strong nuclear force:
  • It is basically an attractive force
  • It is a non-central force (does not act at the centre)
  • It is stronger than gravitational force
  • It is a short-range force that is it operates only up to distance of the order of 10-14m
Properties of the weak nuclear force
  • It is much stronger than the gravitational force but weaker than the strong nuclear force and electromagnetic force
  • It acts on small ranges of up to 10-17m
Activity 1
CLASS ACTIVITY
  1. Define the term force and give its SI unit.
  2. Mention four fundamental types of force that you know.
  3. Define the following terms: Force of gravity; Strong nuclear force; Electromagnetic force.
  4. A body has a mass of 40kg. Find its weight.
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