Newton's Law, Acceleration, Velocity, Force

 

Newton’s Law of Motion

Sir Isaac Newton (1643-1727) an English scientist and mathematician famous for his discovery of law of gravity also discovered the three laws of motion.

 

   Newton’s Laws of Motion

                          

Newton’s First Law: Object in motion tend to stay in motion and objects at rest tend to stay at rest unless acted upon by an unbalanced force.

 

Newton’s Seconds Law: Force equals mass time acceleration (f = ma).

 

Newton’s Third Law: For every action there is an equal and opposite reaction.

 

                           Newton’s First Law

An object at rest tend to stay at rest and object in motion tends to stay in motion unless acted upon by an unbalanced force.

 

                         What does this mean?    

 

Basically, an object will “ keep doing what it was doing ’’ unless acted on by an unbalanced force.

 

If the object was sitting still, it will remain stationary. If it was moving at a constant velocity, it will keep moving.

It take force to change the motion of an object.

 

           What is mean by unbalance force?

If the forces on an object are equal and opposite, they are said to be balanced, and the object experiences no change in motion. If they are not equal and opposite, then the forces are unbalanced and the motion of the object changes.

 

               Some examples from real life

A soccer ball is sitting at rest. It takes an unbalanced force of a kick to change its motion.

 

Two teams are playing tug of war. They are both exerting equal forces on the rope in opposite directions. This balanced forces result in no change in motion.

 

Newton’s First Law is also called the Law of Inertia add to notes

 

Inertia: The tendency of an object to resist change in its state of motion.

 

The first law states that all objects have Inertia. The more mass an object has, the more inertia it has (and the harder it is to change its motion).

 

                           Newton’s Second Law

Force equals mass times acceleration.

   

                      F = ma

 

Acceleration: A measurement of how quickly an object is changing speed.

 

                         What does F = ma mean?

Forces is directly proportional to mass and acceleration.

Imagine a ball of a certain mass moving at a certain acceleration. This ball has a certain force.

Now imagine we make the ball twice a big (double the mass) but keep the acceleration constant. F = ma says that this new ball has twice the force of the old ball.

Now imagine the original ball moving at twice the original acceleration. F = ma says that the ball will again have twice the force of the ball at the original acceleration.

 

                          What does F = ma says?

F = ma basically mean that the force of an object comes from its mean and its acceleration.

 

Something very massive (high mass) that’s changing speed very slowly (low acceleration), like a glacier, can still have great force.

 

Something very small (low mass) that’s -changing speed very quickly (high acceleration), like a bullet, can still have a great force. Something very small changing speed very slowly will have a very weak force.

  

                              Newton’s Third Law

For every action there is an equal and opposite reaction.

 

    Think about it…..

What happens if you are standing on a skateboard or a slippery floor and push against a wall? You slide in the opposite direction (away from the wall), because you pushed on the wall but the wall pushed on the wall pushed back on you with equal and opposite force.

Why does it hurt so much so when you stub your toe? When your toe exerts a force an a rock, the rock exerts an equal forces back on your toe. The harder you hit your your toe against it, the more forces the rock exerts back on your toe ( and the more your toe hurts).

 

Newton’s Laws of Motion Review

 

Newton’s First Law: Objects in motion tend to stay in motion and object at rest tend to stay at rest unless acted upon by an unbalanced force.

 

Newton’s Second Law: Force equals mass time acceleration. (F = ma)

 

Newton’s Third Law: For every action there is an equal and opposite reaction.

 

Vocabulary add to notes

 

Inertia: The tendency of an object to resist change in its state of motion.

 

Acceleration: ^ A change in velocity.

                         ^ A measurement of how quickly an object is changing, and direction.

 

Velocity: The rate of changing of a position along a straight line with respect to time.

 

Force: Push or Pull (strength or energy).