Chapter 9. Force And Law Of Motion
Force : Force is push or pull which change or it has tendency to change the position of body.
In other words;
Applied pushing, hitting and pulling on an object is known as force.
The S.I unit of force is neuton (N) or kgm-2.
It is a vector quantity. It has both magnitude and direction.
Force is caused motion in an object.
Type of forces:
1. Friction force: This is a force which acts opposite to the direction of motion. It acting between to surfaces. Example:
(i) When we walk the force acting between our slipper and the earth.
(ii) When a car runs on the road force acting between tires and the road.
Reducing the friction force:
For reducing or minimising the frictional force we use
(i) Smooth marble
(ii) Smooth plane
(iii) Providing a lubricant on top of the planes
2. Centripital force
3. Magnetic force
4. Gravitational force
Acording to its severity there are two kinds of force is known;
(i) Balanced force : If the resultant of several force acting on a body is zero then force are said to be balanced force.
(ii) Unbalanaced force : If the resultant of several force acting on a body is not zero then force are said to be balanced force.
- If an unbalanced force is applied on the object, there will be a change either in its speed or in the direction of its motion.
- An unbalanced force is required to accelerate the motion of an object.
- The change in the speed (or change in the direction of motion) of object would continue as long as this unbalanced force is applied.
Newton further studied Galileo’s ideas on force and motion and presented three fundamental laws that govern the motion of objects. These three laws are known as Newton’s laws of motion.
(1) The First Law of Motion
(2) The Second Law of Motion
(3) The Third Law of Motion