Wednesday February 1st

Sir Isaac Newton’s Laws: First and Second Laws of Motion

Okay! So what are we doing today?

• Content Objective: Students will be able to summarize the three laws of motion. • Literacy Objective: Students will be

able to define inertia as the tendency of an object to resist a change in its motion

First Law of Motion• The First Law of Motion states that if the

net force acting on an object is zero, the object doesn’t change its motion– If it’s at rest – it stays at rest– If it’s moving – it keeps moving

• Only Unbalanced forces change an object’s velocity

We basically knew all that already!

We basically knew all that already!

Does anyone here HATE change?

• You like things the way they are and you don’t want to change them?

• In humans this iscalled being stubborn

• In objects this is called inertia

Inertia• Inertia is the tendency of an object to

resist change in its motion• ALL OBJECTS HAVE INERTIA, whether they

are moving or not• Inertia means objects hate change• The heavier and object, the more it resists

change– Imagine stopping a sumo wrestler running at

you vs. stopping a horse jockey running at you

What happens in a car crash?

• Let’s test it out with my dear friend, Winnie the Pooh!

Second Law of Motion

• Second Law of Motion – the acceleration of an object is in the same direction as the net force on the object – (whichever way the net force is pointing, that’s

the direction the object moves)

• Force = Mass * Acceleration (F = ma)

Third Law of Motion

• Third Law of Motion: for every action there is an opposite and equal reaction

• A good example is jumping on a trampoline• http://www.youtube.com/watch?v=TK27akn

WVI4

So let’s review the 3 laws:

• First Law: An object in motion tends to stay in motion, an objet at rest tends to stay at rest (unless acted upon by an unbalanced force)

• Second Law: F=m*a, i.e. it takes more force to move a heavier object the same distance

• Third Law: For every action there is an opposite and equal reaction

Visual Review of 3 Laws

• http://www.youtube.com/watch?v=cP0Bb3WXJ_k