Newton’s Laws of Motion

1st Law of MotionO An object at rest will stay at rest and an object in

motion will stay in motion (in the same direction and at a constant speed) UNLESS an unbalanced force is applied.

1st Law of Motion

ExamplesO Can you explain these using the 1st Law of Motion?

1st LawO More simply stated:O If an object is moving, they want to stay

moving.O If an object is still, they want to stay still.O The only way to change what they an object

is doing is to apply a force.

Law of InertiaO Objects are lazy – they do not want to stop what

they are doing.O What can we call this “laziness?”

InertiaO Inertia is a measure of it’s resistance to change.O The more resistant, the more inertia O Newtons’ First Law is also called the

2nd Law of MotionO Usually stated as an equation:

F = ma

O What does this mean?O And don’t say force equals

mass times acceleration. Anyone can say that, but do you really understand what it means?

O What if I restated the equation?

Newton’s 2nd Law Explained

O It means the acceleration of an object depends on two things – the mass of the object and the amount of force you apply to change its motion.

O Let’s look at this relationship.

Let’s Look Mathematically

O If I double the numerator, what happens?

= 4 = 8 4 4

O When one variable increases, another variable increases the same amount.O This is called a direct proportionO Which 2 variables are directly proportional?O What does that mean?

But this is science class!

Math and Science

O What happens when I increase the denominator?

O Let’s try!

O4 = 4 =

O4 8O This is called an indirect proportion, or

inverse proportionO Which 2 variables are inversely

proportional?O What does that mean?

Newton’s 2nd Law

O Look at the equation. Think of the previous fractions. Can you explain what it means now?

2nd Law of MotionO The greater the

applied force, the faster the object will move (acceleration).

O The more mass an object has, the more force you need to change it’s motion

3rd Law of Motion

O For every action, there is an equal and opposite action.

Let’s Review NewtonO Once moving at a steady speed In a straight line It will continue moving At a steady speed In a straight lineO Once standing still It will stay still

NewtonO It accelerates in the direction that

you push it If you push twice as hard, it accelerates twice as much

O If it has twice the mass It accelerates half as much

Newton

O If you push on it It pushes on you

Check out these videosOhttp://science.discovery.com

/interactives/literacy/newton/newton.html

Ohttp://www.fmalive.com/

Questions?