Motion & Newton’s Laws

Earth Systems

A force is…a push or a pull.

Friction, Drag, Gravity, and Weight are forces.

Measured in unit N = kg m

sec2

Background Knowledge continued. . .

Sir Isaac Newton is famous for explaining the motion of object using mathematics.

SPEED: a measurement of distance traveled in a given time. Speed = distance

timeUnits: m/sec

VELOCITY: an objects speed and direction.

Background Knowledge continued.. .

ACCELERATION: Change in velocity Increase in velocity: acceleration Decrease in velocity: deceleration or negative acceleration.

Acceleration: final velocity – initial velocity time

Units: m sec2

Graphing

If Sally got to school on foot and bus describe her movement according to the graph.

•Sally walked to the bus stop at .5 km/min

•She sat waiting for the bus 0 km/min

•She rode the bus at a average speed of

Acceleration “dot diagram” Dot represents an object’s position at different times.

Acceleration: distance increases each second

1 sec

1 sec

5 sec3 sec

7 sec5 sec3 sec

Negative Acceleration / deceleration: distance decreases each second

7 sec

video

http://videos.howstuffworks.com/discovery/29421-assignment-discovery-newtons-laws-of-motion-video.htm Assignment Discovery: Isaac Newton’s Principia

Exploring the laws of motion: Newton’s 1st law Lego video: http://

www.youtube.com/watch?v=NWE_aGqfUDs

1st Law: The Law of Inertia

An object in motion will stay in motion, An object at rest will stay at rest, unless an outside force acts on it.

Newton’s 1st Law rap http://www.youtube.com/watch?v=OaKc4PlrEY8

Larger mass larger inertia Smaller mass smaller inertia Example:

Table cloth trick Penny in a flask Dinosaur riding on hood of car

1st law stated again

If no unbalanced force acts on an object the object will continue moving at the same speed in the same direction

If an object is not moving and at rest the object will remain at rest until an outside force acts upon it.

Friction and gravity are the unbalanced forces that are acting on all the motion that we observe.

Friction is the force that slows things down when two objects rub together.

Friction slows objects until they stop, heats things up and wears them down.

Gravity is the force pulling two objects together

Newton’s 1st Law and You

Don’t let this be you. Wear seat belts.Don’t let this be you. Wear seat belts.

Because of inertia, objects (including you) Because of inertia, objects (including you) resist changes in their motion. When the resist changes in their motion. When the car going 80 m/hour is stopped by the brick car going 80 m/hour is stopped by the brick wall, your body keeps moving at 80 m/hour.wall, your body keeps moving at 80 m/hour.

Inertia = Mass

Bigger masses have more…

Smaller masses have less inertia.

Inertia = Resistance to…

changing speed.

changing direction.

Inertia = resistance to changes in motion.

Large masses

resist net forces and

do not accelerate

much.A large mass resists changing its velocity.

What if we put rockets on each creature?

Large masses resist changing

motion.

Small masses change motion

easily.

2nd Law

Force = mass x acceleration

Animations: \http://videos.howstuffworks.com/discovery/29421-assignment-discovery-newtons-laws-of-motion-video.htm

http://www.youtube.com/watch?v=7_fbH-muvlw&feature=related “Three laws of motion” Assignment Discovery: Newton’s Laws of Motion (

http://videos.howstuffworks.com/discovery/29421-assignment-discovery-newtons-laws-of-motion-video.htm) show for 2nd law

2nd Law

When mass is in kilograms and acceleration is in m/s/s, the unit of force is in newtons (N).

One newton is equal to the force required to accelerate one kilogram of mass at one meter/second/second.

2nd Law (F = m x a) How much force is needed to accelerate a

1400 kilogram car 2 meters per second/per second?

Write the formula F = m x a Fill in given numbers and units F = 1400 kg x 2 meters per second/second Solve for the unknown 2800 kg meters/second/second or 2800 N

3rd Law

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

3rd LawAccording to Newton, whenever objects A and B interact with each other, they exert forces upon each other. When you sit in your chair, your body exerts a downward force on the chair and the chair exerts an upward force on your body.

3rd Law

There are two forces resulting from this interaction - a force on the chair and a force on your body. These two forces are called action and reaction forces.

Newton’s 3rd Law in Nature Consider the propulsion of

a fish through the water. A fish uses its fins to push water backwards. In turn, the water reacts by pushing the fish forwards, propelling the fish through the water.

The size of the force on the water equals the size of the force on the fish; the direction of the force on the water (backwards) is opposite the direction of the force on the fish (forwards).

3rd Law

Flying gracefully Flying gracefully through the air, through the air, birds depend on birds depend on Newton’s third Newton’s third law of motion. As law of motion. As the birds push the birds push down on the air down on the air with their wings, with their wings, the air pushes the air pushes their wings up their wings up and gives them and gives them lift.lift.

Consider the flying motion of birds. A bird flies by use of its wings. The wings of a bird push air downwards. In turn, the air reacts by pushing the bird upwards.

The size of the force on the air equals the size of the force on the bird; the direction of the force on the air (downwards) is opposite the direction of the force on the bird (upwards).

Action-reaction force pairs make it possible for birds to fly.

Other examples of Newton’s Third Law

The baseball forces the bat to the left (an action); the bat forces the ball to the right (the reaction).

3rd Law

Consider the motion of a car on the way to school. A car is equipped with wheels which spin backwards. As the wheels spin backwards, they grip the road and push the road backwards.

3rd LawThe reaction of a rocket The reaction of a rocket is an application of the is an application of the third law of motion. third law of motion. Various fuels are burned Various fuels are burned in the engine, producing in the engine, producing hot gases. hot gases.

The hot gases push The hot gases push against the inside tube of against the inside tube of the rocket and escape out the rocket and escape out the bottom of the tube. the bottom of the tube. As the gases move As the gases move downward, the rocket downward, the rocket moves in the opposite moves in the opposite direction.direction.

Non newtonian fluid

Non newtonian fluid pool http://www.youtube.com/watch?v=f2XQ97XHjVw