Newton's Laws of Motion

Sir Isaac Newton First Law of Motion Second Law of Motion Third Law of Motion Review Newton's Laws Quiz Quiz Answers Hot Wheels Lab Balloon Racers

 

Sir Isaac Newton

Sir Isaac Newton was one of the greatest scientists and mathematicians that ever lived. He was born in England on December 25, 1643. He was born the same year that Galileo died. He lived for 85 years. Isaac Newton was raised by his grandmother. He attended Free Grammar School and then went on to Trinity College Cambridge. Newton worked his way through college. While at college he became interested in math, physics, and astronomy. Newton received both a bachelors and masters degree.
While Newton was in college he was writing his ideas in a journal. Newton had new ideas about motion, which he called his three laws of motion. He also had ideas about gravity, the diffraction of light, and forces. Newton's ideas were so good that Queen Anne knighted him in 1705. His accomplishments laid the foundations for modern science and revolutionized the world. Sir Isaac Newton died in 1727.
In this lesson you will develop an understanding of each of Newton's Three Laws of Motion. 

According to Newton's first law...

An object at rest will remain at rest unless acted on by an unbalanced force. An object in motion continues in motion with the same speed and in the same direction unless acted upon by an unbalanced force. This law is often called "the law of inertia".

What does this mean? This means that there is a natural tendency of objects to keep on doing what they're doing. All objects resist changes in their state of motion. In the absence of an unbalanced force, an object in motion will maintain this state of motion.

Let's study the "skater" to understand this a little better.
What is the motion in this picture?

What is the unbalanced force in this picture?

What happened to the skater in this picture?



This law is the same reason why you should always wear your seatbelt.




Now that you understand
Newton's First Law of Motion,
let's go on to his Second Law of Motion. 

According to Newton's second law...

Acceleration is produced when a force acts on a mass. The greater the mass (of the object being accelerated) the greater the amount of force needed (to accelerate the object).

What does this mean? Everyone unconsiously knows the Second Law. Everyone knows that heavier objects require more force to move the same distance as lighter objects.




However, the Second Law gives us an exact relationship between force, mass, and acceleration. It can be expressed as a mathematical equation:

or
FORCE = MASS times ACCELERATION



This is an example of how Newton's Second Law works:
Mike's car, which weighs 1,000 kg, is out of gas. Mike is trying to push the car to a gas station, and he makes the car go 0.05 m/s/s. Using Newton's Second Law, you can compute how much force Mike is applying to the car.


Answer = 50 newtons


This is easy, let's go on to
Newton's Third Law of Motion 

According to Newton's third law...

For every action there is an equal and opposite re-action.

What does this mean?

This means that for every force there is a reaction force that is equal in size, but opposite in direction. That is to say that whenever an object pushes another object it gets pushed back in the opposite direction equally hard.



Let's study how a rocket works to understand
Newton's Third Law.

The rocket's action is to push down on the ground with the force of its powerful engines, and the reaction is that the ground pushes the rocket upwards with an equal force.

UP, UP, and AWAY!