Newton’s Laws of Newton’s Laws of MotionMotion

How and why do things move How and why do things move the way they do?the way they do?

MotionMotion

In order to prove motion, you must first In order to prove motion, you must first have a point of reference.have a point of reference.

You don’t have to see something move, You don’t have to see something move, you can tell something has moved by its you can tell something has moved by its position according to a reference point.position according to a reference point.

Not all motion is as obvious. You are in Not all motion is as obvious. You are in motion now, not relative to this room or motion now, not relative to this room or your desk, but relative to other planets.your desk, but relative to other planets.

Distance vs displacementDistance vs displacement

When judging motion or position, you When judging motion or position, you must understand the difference must understand the difference between distance and displacement.between distance and displacement.

Distance is how far an object has Distance is how far an object has moved.moved.

Displacement is the distance from the Displacement is the distance from the starting point.starting point.

You can travel a distance of 50 meters You can travel a distance of 50 meters and have a displacement of 0.and have a displacement of 0.

SpeedSpeed

Speed is the determined using the Speed is the determined using the total distance traveled by the total total distance traveled by the total time it takes.time it takes.

S=d/tS=d/t

Velocity Velocity

Velocity is speed in a given direction.Velocity is speed in a given direction. The formula is the same as the formula for The formula is the same as the formula for

speed.speed.

S=d/tS=d/t

Where would velocity be needed?Where would velocity be needed?

AccelerationAcceleration

Acceleration is the rate of change in Acceleration is the rate of change in velocity divided by the amount of velocity divided by the amount of time it takes.time it takes.

(final velocity – initial velocity)(final velocity – initial velocity)

TimeTime

Motion and ForcesMotion and Forces Force is any push or pullForce is any push or pull Balanced force causes no changeBalanced force causes no change

in motion. The net force would in motion. The net force would

be equal to zero.be equal to zero. Unbalanced force will cause a change Unbalanced force will cause a change

in motion. The net force is equal the in motion. The net force is equal the difference between the forces if they difference between the forces if they are in opposite directions, or added if are in opposite directions, or added if the forces are in the same direction.the forces are in the same direction.

InertiaInertia

Inertia is the resistance of an object Inertia is the resistance of an object to change its motion.to change its motion.

Mass is the amount of matter in an Mass is the amount of matter in an object.object.

The greater the mass,The greater the mass, the greater the inertia. the greater the inertia. The greater the inertia,The greater the inertia, the greater the mass.the greater the mass.

Newton’s First Law of MotionNewton’s First Law of Motion

The Law of Inertia states that an The Law of Inertia states that an object in motion stays in motion, object in motion stays in motion, unless acted upon by an outside unless acted upon by an outside force.force.

Law 1Law 1

Newton’s second law of motionNewton’s second law of motion

How mass, force, and acceleration are How mass, force, and acceleration are connected.connected.

The net force of an object causes the object to The net force of an object causes the object to accelerate in the direction of the net force.accelerate in the direction of the net force.

a is acceleration, F is net force, and m is a is acceleration, F is net force, and m is mass.mass.

a = a = FF mm

AccelerationAcceleration There are two formulas for accelerationThere are two formulas for acceleration

1. 1. (final velocity – initial velocity)(final velocity – initial velocity) timetime

2. 2. FF (force)(force) m (mass)m (mass)

The formula you use depends on the information The formula you use depends on the information that you are given.that you are given.

FrictionFriction

According to Newton’s first Law, According to Newton’s first Law, without any opposing forces motion or without any opposing forces motion or lack of motion would remain the same.lack of motion would remain the same.

One force that opposes motion is One force that opposes motion is friction.friction.

Friction increases/decreases Friction increases/decreases depending on the type of surfaces.depending on the type of surfaces.

The stronger the force pushing the The stronger the force pushing the surfaces together, the stronger the surfaces together, the stronger the microwelds.microwelds.

Microwelds are surface bumps.Microwelds are surface bumps.

Static FrictionStatic Friction

If the microwelds that form between If the microwelds that form between the surface and an object trying to the surface and an object trying to be moved are to tight to be broken, be moved are to tight to be broken, then you have static friction.then you have static friction.

Static friction has no net force, Static friction has no net force, therefore there is no acceleration.therefore there is no acceleration.

Sliding frictionSliding friction Sliding friction is the force that Sliding friction is the force that

opposes the motion of two surfaces opposes the motion of two surfaces sliding past each other.sliding past each other.

Sliding friction is caused by Sliding friction is caused by microwelds constantly breaking and microwelds constantly breaking and then forming again as the object then forming again as the object slides.slides.

To keep the object moving, you must To keep the object moving, you must continue applying the force, if you continue applying the force, if you don’t it will stop.don’t it will stop.

Rolling FrictionRolling Friction

Rolling friction is the friction between Rolling friction is the friction between a rolling object and the surface it a rolling object and the surface it rolls on.rolls on.

Microwelds break and then reform as Microwelds break and then reform as it rolls.it rolls.

Rolling friction is usually much less Rolling friction is usually much less than static or sliding friction.than static or sliding friction.

Air ResistanceAir Resistance

Air resistance affects anything that Air resistance affects anything that moves in the air.moves in the air.

Air resistance acts in the opposite Air resistance acts in the opposite direction of gravity.direction of gravity.

The amount of air resistance depends The amount of air resistance depends on the size, speed, and shape of the on the size, speed, and shape of the object.object.

Which falls faster a feather Which falls faster a feather or an acorn?or an acorn?

The Law of GravitationThe Law of Gravitation

Anything that has mass is attracted Anything that has mass is attracted by the force of gravity.by the force of gravity.

Gravity is affected by the mass of an Gravity is affected by the mass of an object, as well as the distance object, as well as the distance between the objects.between the objects.

The greater the mass, the greater the The greater the mass, the greater the force.force.

The greater the distance, the less the The greater the distance, the less the force.force.

Gravitational AccelerationGravitational Acceleration Near the Earth’s surface the gravitational attraction Near the Earth’s surface the gravitational attraction

cause objects to accelerate at the rate of 9.8m/scause objects to accelerate at the rate of 9.8m/s22

According to Newton’s second law of motion, force, According to Newton’s second law of motion, force, mass, and acceleration are related according to the mass, and acceleration are related according to the following formulafollowing formula

F=maF=ma

Gravitational AccelerationGravitational Acceleration

According to the second law, the According to the second law, the force of an object that has an force of an object that has an acceleration of 9.8m/sacceleration of 9.8m/s22 is as follows- is as follows-

F= m x 9.8m/sF= m x 9.8m/s22

This force depends on an objects This force depends on an objects mass.mass.

WeightWeight

Weight is a response to Weight is a response to

the amount of gravity. the amount of gravity. Since the gravitational force is the same Since the gravitational force is the same

as the weight of an object, the equation-as the weight of an object, the equation- F= m x 9.8m/sF= m x 9.8m/s22

can also be written-can also be written- W= m x 9.8m/sW= m x 9.8m/s22

What would happen to your weight as you What would happen to your weight as you get farther away from Earth’s surface?get farther away from Earth’s surface?

Weight and MassWeight and Mass

Since mass is the amount of matter Since mass is the amount of matter in an object, and weight is the force in an object, and weight is the force of gravity on an object, of gravity on an object,

1. How does your mass change on 1. How does your mass change on the moon?the moon?

2. How does your weight change on 2. How does your weight change on the moon?the moon?

Projectile motionProjectile motion

A projectile is anything thrown or A projectile is anything thrown or shot through the air.shot through the air.

Knowing what you do about the Knowing what you do about the gravitational force, when shooting at gravitational force, when shooting at a target like a dart board, where a target like a dart board, where should you aim?should you aim?

Vertical and Horizontal MotionVertical and Horizontal Motion Throwing a ball is horizontal motion.Throwing a ball is horizontal motion.

Dropping a ball is vertical motion.Dropping a ball is vertical motion.

Throwing a ball forward it always Throwing a ball forward it always lands on the ground eventually. lands on the ground eventually. Why?Why?

Centripetal ForceCentripetal Force

Acceleration towards the center Acceleration towards the center

of a curved or circular path, is of a curved or circular path, is

centripetal acceleration.centripetal acceleration. When a car rounds a corner,When a car rounds a corner, centripetal force is the friction centripetal force is the friction between the tires and the road.between the tires and the road. Planets traveling around the Planets traveling around the

sunhave centripetal force. sunhave centripetal force. Explain why.Explain why.

Newton’s Third Law of MotionNewton’s Third Law of Motion

Action/ReactionAction/Reaction For every action in nature there is a For every action in nature there is a

reaction.reaction.

If action and reaction forces are equal If action and reaction forces are equal and opposite, why or how is there and opposite, why or how is there motion.motion.

MomentumMomentum Momentum is the force needed to change Momentum is the force needed to change

motion.motion. To determine momentum, you take the mass To determine momentum, you take the mass

of an object of an object

times the velocity of an object.times the velocity of an object.

Momentum is given the symbol pMomentum is given the symbol p

p=m x vp=m x v

Law of conservation of momentumLaw of conservation of momentum

According to Newton’s Laws, According to Newton’s Laws, momentum can’t be lost or gained, momentum can’t be lost or gained, only transferred.only transferred.

What does this mean?What does this mean?

ReviewReview

1. An object in motion remains in motion 1. An object in motion remains in motion unless acted upon by an outside force.unless acted upon by an outside force.

2. Acceleration is the net force of an 2. Acceleration is the net force of an object divided by the mass of an object.object divided by the mass of an object.

3. For every action there is an equal and 3. For every action there is an equal and opposite reaction.opposite reaction.

Let’s see it again!Let’s see it again!

How do these affect us in everyday How do these affect us in everyday life?life?

Now that you know these laws, here Now that you know these laws, here are some ways that they affect us in are some ways that they affect us in everyday life.everyday life.

Show me!Show me!

Can you think of examples?Can you think of examples?