Mr. Finau Applied Science III

What does the phrase “Everything’s relative” mean?  Observations come from a perspective  Every perspective can reveal a different conclusion

What does the phrase “Motion is relative” mean?  Motion depends on your perspective  An object can appear to be moving from one perspective, but not from another

Distance & Displacement

What is Speed? What is Velocity? What’s the difference?  Speed is the rate at which an object moves  “How fast an object moves”  Velocity is the rate at which an object changes position  “How fast an object moves & what direction”  Speed gives you an amount; Velocity gives you an amount and direction

What are the units for speed/velocity? Can you come up with an equation for it?  In metric, we use meters/seconds (m/s)  A rabbit runs 10 m in 2 seconds. How fast does it run?  A squirrel runs with a speed of 4 m/s. How far does it travel in 2 seconds?

What is the “ultimate speed limit”…the fastest speed that we know of?  Speed of Light  3 X 10 8 m/s  Over 671 million miles per hour!!!

What is acceleration? Where do you use acceleration in your life?  Acceleration is the rate at which velocity changes  Examples?  Start running from stopped position  Sliding into 2 nd base in baseball  Driving a car – push on accelerator, brake, or turn the wheel

What’s the difference between acceleration and velocity  Velocity is the change in position over a period of time  Acceleration is the change in velocity over a period of time

An apple falls from a tree; does it accelerate? Why?  Yes, a falling apple accelerates  Its speed changes from zero to moving…  Gravity causes acceleration vertically

What is free fall? How much do you feel like you weigh when you’re in free fall?  Free fall is when an object is only acted upon by gravity  You feel weightless  Is there a difference between Weight & Mass?  Yes, mass is the amount of matter, weight depends on gravity

A ball is thrown vertically upward. What happens to the ball’s velocity while it’s moving upward?  The ball slows down as it moves upward

What is its velocity when it reaches its maximum height? What’s happening to the direction the ball is moving at this point?  Velocity is zero; stops moving for a brief moment  The ball’s velocity is changing direction

What happens after the ball changes direction? What causes this?  Starts moving downward  Gravity pulls the ball downward

At what part(s) of the ball’s flight is it accelerating?  The ball accelerates during all parts of its flight

If an object has a positive acceleration, what is happening to the object velocity and distance traveled?  Velocity increases (at a constant rate)  Distance increases (exponentially)  Exponentially – travels farther & farther each second

If an object has a negative acceleration, what is happening to the object velocity and distance traveled?  2 possibilities:  Velocity is decreasing  Distance still increasing  Velocity is increasing in negative direction  Distance increases in negative direction

If a turtle slides across the beach with a constant speed of.25 m/s, what is its acceleration?  Acceleration = O  Key words – Constant Speed

If a car is traveling eastward, can its acceleration be in the westward direction? How?  If a car is slowing, it has a negative acceleration.  If eastward is in the positive direction, what’s in the negative?  Westward, so Yes!

Graphing Motion

Situation  Let’s discuss in terms of a car that is driving with a constant acceleration of 1 m/s 2

Keys to Graphing Motion  Identify which variable is the dependent variable  This is the variable on the y-axis  will change depending on independent variable on x- axis(usually time)

Keys to Graphing Motion  Determine what the dependent variable is doing  Whether it is:  Zero (no value; there is none)  Staying Constant (value doesn’t change)  Increasing/Decreasing at a constant rate (typically just a diagonal)  Increasing/Decreasing exponentially (typically a curve)

Keys to Graphing Motion  Understand what is happening to object  Imagine what the object is doing in relation to the dependent variable  Three Variables:  Distance  Velocity  Acceleration  For example – if velocity is constant, you know acceleration is zero, and distance will increase at constant rate

Keys to Graphing Motion  Describe/Graph the other variables vs time  Be able to fully describe what is happening to the other variables of the object  If you’re given velocity, be able to describe what is happening to its distance and acceleration

Back of Worksheet Given: _________________ Describe other variables

Review – Quiz tomorrow  Review your notes carefully  Any questions in particular?  Remember Speed equation – 3 math questions  Hint to remember  mph = miles/hours  Review how to graph when discussing distance & velocity – 2 graphing questions