Newton’s Laws of Motion

1st Law of Motion

INERTIA An object will

remain at rest or in constant motion unless acted upon by an unbalanced force.

“THE OLD TABLECLOTH TRICK”

How does this comic relate to Inertia?

Mass- the amount of “stuff” or matter in an object

WHICH HAS MORE MASS? WHICH HAS MORE MASS?

Do All Objects Have the Same Inertia?

LESS MASS = LESS INERTIA

The skier does not have a lot of mass therefore has LESS inertia; & is easier to stop

MORE MASS = MORE INERTIA

The car has MORE MASS therefore has A LOT OF INERTIA; & is harder to stop

Penny in Cup Demonstration•Finger applies a force to a card causing it to move•Penny STAYS at rest (over the cup) due to inertia•Gravity causes the penny to fall into cup

Spinning Eggs Demo

What happened to the spinning hardboiled egg when you tapped it? The egg stopped

spinning

Why? The egg is a solid unit

and the finger applied enough force to change the inertia

What happened to the spinning raw egg when you tapped it & let go? The egg continued to

spin

Why? The liquids inside the

egg were in motion & wanted to stay in motion due to inertia

Cups & Paper Towel

Which cup was easier to keep standing? The cup (more massive one) because it

has more inertia

The empty cup was harder to keep standing because it has less mass therefore less inertia

Think, Pair, Share1.) What will happen to the bone or stick if the

forces acting on it are not equal?2.) What direction will the bone or stick move?

“Bullies in a Box” showing Newton’s Laws of Motion

Vectors- arrows that show the direction & strength (magnitude) of a force

•Longer Arrow = Stronger Force•Shorter Arrow = Weaker Force•Forces measured in Newtons (N)

Balanced Forces- equal in strength & opposite in direction

Cancel each other out so net force = O

Results in NO MOTION or NO CHANGE in motion

Unbalanced Forces

Forces that don’t cancel & the object moves in the direction of the stronger force.

DIFFERENT directions, SUBTRACT the forces

SAME direction, ADD the forces.

Practice finding the Net Force…

Determining the Net Force…

2nd LawF= ma

An object acted on by an unbalanced force accelerated in the direction of the force

F=ma???? What does it mean? Force= mass x

acceleration

Mass (kg or grams)

Acceleration (m/s2) 1 Newton= force

needed to move 1 kg 1 m/s2

Gravity-force of attraction between objects; depends on mass & distance between them

More Mass = More Gravity Earth has more

gravity than Moon b/c Earth is more massive

More Distance = Less gravity

Acceleration due to Gravity = 9.8 m/s2

Mass vs. Weight…What’s the Difference?