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# Newton's Laws of Motion (Grade 8)

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## Jenn Wilson

on 27 October 2014

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#### Transcript of Newton's Laws of Motion (Grade 8)

Newton's First Law of Motion
Also known as the...
Law of Inertia
Stated: An object at rest will remain at rest and an object in motion will continue in motion in a straight line unless acted on by an outside force.
This can be difficult to see on Earth!
because of friction and gravity
friction
a force that opposes motion
air friction
water resistance
surface friction
Where would Newton's First Law (Law of Inertia) be easier to see?
Imagine floating through space. You just happen to be eating m&m's. You try throwing an m&m away from you. That m&m will travel in the same direction in a straight line at a constant speed until acted on by an outside force.
Check this out!!
Don't forget to buckle up!
Objects in motion want to continue in motion.

Objects at rest will stay at rest unless acted on by an outside force... like a golf club.
An object at _________ will stay at _______
and an object in ____________ will continue in
____________ in a _____________ line unless acted on by an outside __________.
Also known as Law of _______________
Watch how Newton's First Law of Motion comes into play with billiards.
The thermal images show how friction transfers energy as heat (the felt glows because the spin of the billiard ball)
ok... one more (a golf ball shot into steel at 70,000 fps)
This is the conclusion of Newton's First Law...
Newton's Laws of Motion Preview
Inertia: The resistance of an object to make a change in motion.
Also known as air resistance or drag.

Aerodynamics: A field of fluid dynamics that studies how gases, including air, flow and how forces act upon objects moving through air.
Hydrodynamics: A field of fluid dynamics that studies how liquids, including water, flow and how forces act upon objects moving through liquids.
Any time two surfaces come in contact there is friction...

Friction can be both good or bad
changing the oil in a car is good.

not changing the oil in a car can be very bad.
sand paper can increase or decrease the amount of friction.
can you think of one example for each?
Slip n' Slides are always good friction.
Ways to reduce friction
Lubrication: Oil, Soap, Grease
Make surfaces smoother
Decrease force between surfaces
Ways to increase friction
More force between surfaces
Make surfaces rougher
Rolling Friction
vs.
Sliding Friction
Surface Matters!
Newton's second Law of Motion states that the bigger something is (its MASS) the more force is required to push it... so when we stat e it mathematically it looks like
Force= Mass x Acceleration
Force = (Mass)(Acceleration)
Have you ever gone around a sharp turn while sitting in the back seat of a car? If you're not wearing your seat belt, what happens?
Momentum: A product of an objects Mass times its Velocity
Formula for Momentum

P = MV
Law of Conservation of Momentum
Law of Conservation of Momenutm states that momentum is not DESTROYED, it is either TRANSFERRED or ABSORBED.
Why are smaller, lighter cars more dangerous to drive in?
Larger cars can crash into them transferring lots of momentum and force equaling more damage.
How does an increase in mass influence momentum?
Increase in mass = increase in momentum.
An increase in the angle = an increase in velocity, which increases momentum
How does an increase in the angle influence momentum?
A
B
A
B
The NEWTON is the unit of measurement for Force
Newton's Third Law of Motion
Every action has an equal
and opposite reaction.

A force is a push or a pull upon an object that results from its interaction with another object.
Forces always come in pairs -
equal and opposite
action-reaction force pairs.
A free falling object is an object that is falling under the sole influence of gravity. Any object that is being acted upon only be the force of gravity is said to be in a state of free fall. There are two important motion characteristics that are true of free-falling objects:

1. Free-falling objects do not encounter air resistance.
2. All free-falling objects (on Earth) accelerate downwards at a rate of 9.8 m/s/s
It takes more Force to push a FULL shopping cart (more mass) than an empty one.
Now you know all about Newton's
Laws of Motion!

I hope you took great notes!
Four Types of Friction:

Static Friction- this is the friction that acts on objects which are not moving... because of static friction, you must use extra force to start the motion of an object

Sliding Friction- occurs when two solid surfaces slide over each other

Rolling Friction- when an object rolls across a surface this type of friction is easier to overcome than sliding friction

Fluid Friction- occurs when a solid object moves through fluid also easier to overcome than sliding friction
These students get it....
STOP and Check for Understanding
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