Motion and Forces

Student Success Statements:

• 8.6C - investigate and describe applications of Newton's three laws of motion such as in vehicle restraints, sports activities, amusement park rides, Earth's tectonic activities and rocket launches

Students will be able to:

• Define Newton’s law of inertia and identify it in several situations, for example in car crashes

• Understand the interaction between inertia andmass

• Know the different forces that affect movement, such as friction and air resistance

Newton’s Laws of Motion

•1st Law – Law of Inertia

•2nd Law – Law of Force and Acceleration

•3rd Law – Law of Action – Reaction

Everything to do with motion, forces, gravity, speed, or acceleration is governed

by these laws.

Motion

Many of the objects we encounter in everyday life are in motion or have parts that are in motion, even down to the atomic level. Motion is the rule of all objects, not the exception. The physical laws that govern the motion of these objects are universal, i.e. all the objects move according to the same rules.

Newton’s First Law of Motion“Law of Inertia”

•An object at rest (not moving) will stay

at rest unless acted upon by an external

force.

Newton’s First Law of Motion“Law of Inertia”

•An object in motion

will stay in motion

unless acted on by

an unbalanced force

What happens when a car hits a stationary object?

What happens to you riding in that car?

Inertia

Bike Race Crash

So, what happened to the biker?

Inertia is the Law!

• Inertia is the tendency of an object to keep doing what it's doing unless acted on by an unbalanced force.

• It RESISTS change!

• The law states - An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted on by an unbalanced force.

•Objects with a greater mass have greater inertia

• Example: It is more difficult to change the motion of bowling ball than the motion of a golf ball

Inertia and mass

Why?

• The bowling ball is much heavier (it has more mass) than the golf ball. So it can resist a change in its motion more than the golf ball.

• It takes more force to move the bowling ball and also to stop it

Forces that act on Motion

• Newton’s First Law of Motion states that an object in motion will stay in motion unless acted on by an “outside force”.

• Two forces that act on objects are friction and gravity.

Friction Friction acts in a direction

opposite to the object’s direction of motionWithout friction, the

object would continue to move at a constant speed forever

The strength of the force of friction depends on these factors: 1. the types of surfaces

2. how hard the surfaces push together.

Starting a fire

Racing on ice

Types of Moving Friction1. Sliding Friction – solid surfaces

slide over each other.

2. Rolling Friction – when an object rolls over a surface.• Force of friction is less in

rolling friction than with sliding friction.

3. Fluid Friction – when an object moves through a fluid.• Force of friction is less in

fluid friction than with sliding friction.

Gravity• Gravity – is the force that pulls objects toward

each other. The larger object (more mass) has more gravity.

Air ResistanceObjects falling through

air experience a type of friction called air resistanceAs surface area

increases, air resistance increases.

Eventually, air resistance equals gravity

Air ResistanceThe greatest velocity an object reaches is called

terminal velocity. Terminal velocity is the final speed of an object.

Air resistance is offsetting the weight of the object

Drag = air resistance

Summary video:

Why do we wear seat belts?

Inertia and Car Crashes

Video Questions –

• When the truck began moving, the crash dummy fell off the back. What is the property of matter that caused the dummy to resist a change in motion?

• Isaac Newton's First Law of Motion states that an object at rest remains _______ unless acted upon by an external force.

• Isaac Newton's First Law of Motion also states that a body in motion continues to move at a constant _______ in a straight line unless acted upon by an external force.

KNOW the forces involved!!

• P.206 in the textbook

Newton’s Laws –Inertia Lab

The lab is at the end of your notes

Lab Behavior expectations:• Use Principled and on-task behavior, do not

disrupt someone else’s learning opportunity

• Communicate with your group and work on the ATL skill of communication

• Build your towers on the floor – it works better!

• When asked to clean up the lab, put supplies back where you retrieved them from.

• DO NOT turn this in, put the notes in your binder

Lab Questions and Wrap up:

• Answer the questions in complete sentences.

• PAY ATTENTION to the command terms!

• Everyone will work together to put the supplies back and clean up the room.

• When you are ready to leave, stand behind your pushed in chair

• I will dismiss you when everyone is ready