Dynamics

While  Kinematics is that branch of physics which involves the description of motion, it does not examine the cause of motion.

Dynamics, on the other hand, involves an examination of both a description of motion and the forces that produce it.

3.1 Forces in Action

A force is either a pull or a push upon an object resulting from the object interaction with another object.

For example, the man is interacting with the car. He applies a force to push the car, causing it move. The Car in turn will exert force on the man's hand, called reaction force, which prevents the man's hands from sinking into the car's body. 

This interaction between objects does not end here. The car also interacts with the ground. As the car presses down on the ground, the ground pushes up on the car.

Unit of Force

The SI unit for force is newton, its symbol is N.

Was Sir Issac Newton the first person to see an apple falling from a tree? Probably not, but he would have likely been the first to actually question why it fell.
He was probably the first to decide that he wanted to know "Why?" and Persevered to find out the cause. This led to his famous works on the laws of universal Gravitation.


Force Measurement

To measure force in Science laboratory, we use the spring balance to pull the object of interest and measure the steady force registered.

measuring friction

We Can use spring balance to measure the friction between two surfaces. It Can also be used to measure the force required to pull (Open) the door.

To measure the Weight of an object, we hang the object of interest below the spring balance, and allow the pull of gravity to do its work.

In this way, the pull of gravity is measured as the weight of the object.