Chapter 2 – Lesson 2

http://ed.ted.com/lessons/joshua-manley-newton-s-3-laws-with-a-bicycle

Newton’s 1st LawAn object at rest tends to stay at rest and

an object in motion tends to stay in motion unless acted upon by an

unbalanced force.

Part 1: An Object at RestIdentify an object at rest

Ex: chair on the floor, a plane on a runwayThese objects will not start moving until a

is exerted on them.Ex:

push or pull

You tend to fall backward when your school bus starts to move.

Part 2: An Object in MotionAn object moving at a certain velocity will

continue to move at the same speed and in the same direction unless some acts on it.

http://www.physicsclassroom.com/mmedia/newtlaws/il.cfm

unbalanced force forever

Ex: Riding in your car. When your mother or father comes to a stop then you would continue to move, however your seatbelt stops you.

Balanced Force

Equal forces in opposite directions produce no motion

Unbalanced ForceUnequal opposing forces

produce an unbalanced forcecausing motion

If objects in motion tend to stay in motion, why don’t moving objects keep moving

forever?Things don’t keep moving forever because there’s

almost always an acting upon them.A book sliding across a table slows down and stops

because of the force ofIf you throw a ball upwards it will eventually slow down

and fall because of the force of

unbalanced force

gravity

friction

InertiaThe tendency of an object to

resist a change in its motion

Inertia can be described as the tendency of an object to keep doing whatever’s it’s doing.

InertiaInertia is the reason objects at rest and

objects in motion

Inertia is the reason you slide toward the side of a car when the driver makes a sharp turn.

remain at rest remain in motion

MASS and INERTIAThe more an object has, the more

the object has.Therefore an object with a small mass will have

a inertiaAnd an object with a large mass will have a

inertia.Bigger objects are to start & stop

MASS INERTIA

HARDER

Which vehicle has more inertia?

SMALL

LARGE

Inertia

The truck is in motion. What is the force that causes it to stop?

The car is at rest. What is the force that causes it to move?

The push of the stopped car.

The push of the truck.

Group Work!In your group take 3 MINUTES to come up with

an example of Newton’s 1st Law in everyday life. Be ready to explain using the proper vocabulary.

Assess Your KnowledgeIf gravity between the Sun and Earth suddenly

vanished how would Earth move?

Answer: In a straight path

To say that 1kg of matter weighs 10 N is to say that 1kg of matter

a. Will weigh 10N everywhereb. Has less volume than 10kg of matterc. Has more inertia than 10kg of matterd. Is attracted to Earth with 10N of force

Answer: D

If the net force on an object is zero then the object has

a. Balanced forcesb. Action forcesc. Reaction forcesd. Unbalanced forces

Answer: A

The greater the mass of an object,

a. The easier the object starts movingb. The more space the object takes upc. The greater its inertiad. The more balanced it is

Answer: C