Newton’s Three Laws

Isaac Newton

• Sir Isaac NewtonScientist and Mathematician

• 1642 – 1727

• He defined the laws of motion and universal gravitation, which he used to predict precisely the motions of stars, and the planets around the sun.

• “If I have been able to see further, it was onlybecause I stood on the shoulders of giants.”

                                                                —Sir Isaac Newton

Athletes use spinning, pushing and bumping motions to score points.

• Can you think of some examples?

Newton’s First Law of Motion

• 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.

Real World Examples…

• Soccer

If I kick a soccer ball towards the net and the goalie is not there to stop it…

GOAL!!!

• Bowling

When I roll the bowling ball down the lane, it will keep going until it hits the pins… or the gutter!

Newton’s Second Law of Motion

• 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 unconsciously knows the Second Law. Everyone knows that heavier objects require more force to move the same distance as lighter objects.

How Do We Measure it?

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

FORCE = MASS x ACCELERATION

Real World Examples

• If you are a defensive lineman, who would you rather tackle…

A running back that weighs 100 pounds or a running back that weighs 300 pounds?

Newton’s Third Law of Motion

• 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.

In the Real World…

• Golf

When Tiger Woods hits the golf ball…what is the reaction?

• Racing

• When Dale Earnhardt steps on the gas pedal, what is the reaction?

• Now that I’ve given you a few examples, I want you to think of one example of each of Newton’s Three Laws of Motion from sports.