- Force is a push or a pull on an object.
- It changes or tends to change the state of rest or the state of motion of an object by a push or pull.
- It cannot be seen, but its effect can be seen or felt.
- It is caused by an interaction.
- An interaction of one object with another object produces a force between the two objects.

REST: An object is said to be Rest, if it does not change its position with respect to surrounding.

Example: A stationary object kept on a table.

MOTION: If its Position changes continuously with the surrounding then the object is said to be in Motion.

Example: A ball moving from one position to the other with the application of force.

SI UNIT: Standard International Unit.

It is an International system of Measurement that is Universally accepted for scientific purposes.

F= ma

Where M= Mass of an object

a= acceleration produced by an object

Thus, SI unit of Force is Kg m/s^{2 }or Kg ms^{-2}

^{ }Kg ms^{-2 }= Newton.

Thus,

1 Newton is defined as the force which can make an object of 1-kilogram mass to accelerate at the rate of 1 metre per second square. (1m/s^{2})

**CHARACTERISTICS OF FORCE**

- Force has both Magnitude and Direction.
- It states that every object when applied force has the tendency to change its position, shape and nature of object thus the Quantity of O

- The Magnitude in general can be the Number like 4N is the magnitude of force applied.

- Every object on which force is applied either comes to rest of move in a particular direction or can change the direction, thus o application of Force the direction can be known, so Force gives Direction also.

- The quantities that gives both Magnitude and Direction are called VECTOR QUANTITY.

- Thus, Force is a vector quantity.

- Force applied on an object in the same direction add to one another.

- On applying a Force of 5N on an object, the object moves in the direction of force applied.
- Similarly, when forces are applied in one direction they are always added and thus the Resultant/net force can be calculated.

- It is due to the resultant /net force an object tends to be in Motion or rest.

- Since, Force is acting in the same direction so the Net force will be sum of the forces i.e.

8N + 6N = 14N. and it will move in the East direction, that is in the direction of Force applied.

- In this situation, the force is being applied in two different direction, thus the force which is of higher magnitude that will reduce the effect of the lower magnitude.
- If the two forces act in the opposite direction on an object, the net force acting on it is the difference between the two forces.

**BALANCED FORCE**

- Balanced forces are those two forces acting in opposite directions on an object, and they are equal in size.
- Anytime if there is a balanced force on an object, the object stays still or it continues moving at the same speed and in the same direction is called a balanced force.

**UNBALANCED FORCE**

- Unbalanced Force occurs when one force is greater than the other force in the opposite direction.
- Unbalanced force can cause object to speed up, slow down, change direction.

CHECK YOUR KNOWLEDGE

Q1. Define the following:

- Force
- SI unit
- Balanced Force
- Unbalanced Force

Q2. An object can produce an acceleration of 10 ms^{-2} and the mass of the object is 40 kg, Calculate its Force.

Q3. What are the Characteristics of Force?

Q4. Why force can be called as a vector quantity.

Q5. When can be an object be at rest and when can an object be at motion?

Q6. The mass of an object is 500 gram and the force applied on it is 5 N. Calculate the acceleration produced by the object.

Q7. What are the criteria required for the application of force?