Newton’s law of motion
Newton’s First law:
“Every body continues in its state of rest or of uniform motion in a straight line unless it is compelled to change the state by forces impressed on it.
Linear momentum (P) :
The product of mass and velocity of a body is called Linear momentum. P = mv
Newton’s second law of motion:
“The rate of change of momentum of a body is directly proportional to the net external force acting on the body and takes place in the direction in which the force acts” is the statement of Newton’s second law. Newton second law measures Force.
Derivation:
Let the velocity of a body of mass m changes from u to V under the action of force F for time interval .
According to the Newton’s second law,
Example Problem 1:
Calculate the time needed for a net force of 5N to change the velocity of a 10kg mass by 2m/s.
- A) Given, force F=5N, mass m=10Kg, change in velocity = 2m/s
Example Problem 2:
A bullet of mass 0.04Kg moving with a speed of enters a heavy wooden block and is stopped after a distance of 60cm. What is the average resistive force exerted by the block on the bullet?
Newton’s third law of motion:
“To every action there is always an equal and opposite reaction” is the statement of Newton’s third law.
According to Newton’s third law, Action = – (Reaction)
Action and reaction never act on the same body.