Is force a scalar quantity or a vector quantity?
Force is a vector quantity as it has a magnitude as well as direction.
For example, if we wish to move a block to the right, we have to apply a mechanical force in the rightward direction. We cannot apply the force in any direction. Also, since the force being applied is to the right, the block will not move in any other direction other than rightward. This means that magnitude alone cannot define a force. Force has direction too. Hence, it is a vector quantity.
Introduction to Free-body diagram
The forces acting on an object can be represented with the help of a diagram. It tells us not only the direction in which the object will move but also whether the forces are balanced or not. These 2-D dimensional diagrams are known as Free-body diagrams.
Consider a rectangular block kept on the ground. There are two forces at play here –
the weight of the block acting vertically downwards because of the gravitational force, and the normal force of the ground acting vertically upwards.
When we push the block to the right with a force of say 5N, there are two additional forces acting on it. The frictional force between the ground and the block acts in a leftward direction, and the air resistance between the block and the air surrounding it, in the leftward direction as well.
Given below is the free body diagram of the above example. The arrows represent the forces. The size of arrows represent the magnitude of the forces and the direction of the arrows represent the direction of the forces.
Free body diagram of a rectangular block
The object does not move upwards or downwards. Which means that the normal force and gravitational force are equal in magnitude and cancel each other. Hence, the 2 arrows are equal in size.
Also, when we apply the force, the object moves to the right. Which means the magnitude of the push force is greater than the sum of the magnitudes of the forces of friction and air resistance. Hence, the arrow representing the push force is greater in size compared to the 2 forces.
We will learn about these diagrams in detail in the next segment.