WE’RE DONE WITH CHEMISTRY! NO MORE: Chemical Equations Writing Formulas Periodic Table Cations & Anions …

Bellwork Define physics Define motion Define speed Define velocity

Section 1 – Measuring Motion Chapter 10: Motion Section 1 – Measuring Motion

Physics: It Explains the Universe Definition: physics – the study of interactions between matter and energy. The science of physics is used to explain almost every common event: And the concept of MOTION is extremely important in physics!

Definition: motion - an object’s change of position over time. Motion may seem to be very simple, but there are scientific concepts that can explain it. Definition: motion - an object’s change of position over time. There are two ways to measure how far an object has changed position: Distance & displacement

Definition: distance - a measure of the entire path of an object. Definition: displacement - a measure of an object’s change in position from start to end. Displacement is ALWAYS a straight line!

Distance vs. Displacement

We can also measure how fast an object changes it’s position… Definition: speed – the measure of how fast an object is moving. Speed equals distance/time (s = d/t) The SI Unit for Speed is meters per second: (m/s) Americans usually measure speed in mph (miles per hour) Mph OR mi/h

Velocity is calculated the What in the world is velocity? Definition: velocity – the speed of an object in a certain direction. Velocity always has a direction! Velocity equals distance/time (v = d/t) Velocity is calculated the same way as speed!

It’s actually just common sense. The velocity (speed) of an object measures how quickly it is changing position. For example: a speed of 10 m/s means that the object will move 10 meters after one second. A speed of 60 mph means that an object will move 60 miles in one hour. It’s actually just common sense.

Examples Lets look at an examples… A runner runs 50 meters East in 10 seconds. d = 50 m t = 10 s v = d/t = 50 m / 10 s v = 5 m/s East EASY. AS. PIE.

Examples Lets look at an example… A biker is riding north. After 10 seconds, he has gone 100 meters. d = 100 m t = 10 s v = d/t = 100 m / 10 s v = 10 m/s North EASY. AS. CAKE.

Bill Nye – Motion https://www.youtube.com/watch?v=KgmWR3qjXZs Write down 20 facts from beginning to end and turn in for grade

Speed and Velocity https://www.youtube.com/watch?v=dKDDrnx-Fgw

Section 2 - Acceleration Chapter 10 Section 2 - Acceleration

You may not realize it, but you are familiar with the term “acceleration”… Definition: acceleration – the change in velocity over time. Acceleration has the derived unit of m/s2. (meters per second squared) An object accelerates when it speeds up OR slows down.

Acceleration tells how quickly an object is changing velocity. So, you need the change in velocity over a time period. Acceleration = (final velocity minus initial velocity, divided by time.) a = (vf – vi) t

Seriously, what IS acceleration? Think of it like this…when you accelerate… You are moving more or less m/s for every second that passes.

What IS acceleration? So, if you began with a velocity of 10 m/s north… and you had an acceleration of 2 m/s2 N, then that means… For every 1 second that passes, you are moving 2 m/s faster!

What IS acceleration? So, after 5 seconds, you are moving 10 m/s faster the new velocity would be 20 m/s N It’s not a hard concept to understand

Examples Lets look at an example… A biker is riding north at a velocity of 3 m/s. After 10 seconds, his velocity has changed to 8 m/s north. What was his acceleration? vi = 3 m/s north vf = 8 m/s north t = 10 seconds a = = = EASY. AS. CAKE. 8 m/s – 3 m/s 10 s 5 m/s 10 s .5 m/s2

Acceleration can be a negative number. This means that the velocity is decreasing. (the object is slowing down) It could also mean that the object is “speeding up” in reverse. You have a negative acceleration when you apply the brakes and slow down at a stop sign.

Object that have a constant velocity have no acceleration. If the velocity isn’t changing, then there is no acceleration! Objects with a constant acceleration are speeding up by that much each second. In other words…moving faster & faster & faster…

Acceleration is also a change in direction. Since velocity involves speed & direction, acceleration must involve direction also. Definition: centripetal acceleration – the constant change of direction of an object moving in circles. An object can be moving at the same velocity when traveling in a circle, but it’s direction is always changing. So, it is accelerating!

Acceleration and Deceleration https://www.youtube.com/watch?v=uWkTV3ejTc4

Bill Nye - Friction https://www.youtube.com/watch?v=blqlyMkv2Ng

Section 3 – Motion & Forces Chapter 10: Motion Section 3 – Motion & Forces

What is a force? The term force is used all the time, but it can be hard to describe… Definition: force – a push or pull that makes an object accelerate. Forces have directions!

An object can only change its direction when a force is applied to it! Some examples of forces: Gravity Friction Electric Force Nuclear Force Magnetic Force Centrifugal Force Centripetal Force

Circular Motion Forces Definition: centripetal force – pulls an object toward the center of rotation. Definition: centrifugal force – moves an object away from the center of rotation.

This object won’t move anywhere! There are two “types” of forces: Balanced and Unbalanced. Definition: balanced forces – a pair of forces that are equal and opposite. Balanced forces cannot change an objects acceleration. When 2 forces cancel each other out, they are balanced. Object This object won’t move anywhere! Force A Force B

This object will move to the right! Definition: Unbalanced forces – a pair of forces in which one force is stronger than the other. Unbalanced forces cause objects to accelerate. Object This object will move to the right! Force A Force B

Friction is a force present when any two objects are in contact. Definition: friction – a force that causes resistance to motion when objects are in contact. Friction tries to slow down moving objects.

Friction can be described as static or kinetic. Static friction exists between two objects that are not moving. Kinetic friction exists between two objects that are in motion.

Friction comes in several great-tasting flavors: Dry Friction: between two solid surfaces. Sliding Friction – one object is forced to move across another. Rolling Friction – an object rolls across a surface. Fluid Friction: involves a liquid or gas. Air friction – between a gas & a liquid or solid.

Sliding Friction! Rolling Friction! Air Friction!

Friction isn’t always a BAD thing.