Graphing, scalars, vectors, problem solving Monday, August 31, 2015

Monday, 8/31 Unit1: Tools for Physics If this is your first time to class come see me at the door and show me your schedule. Respond to the following on your warm-up: Draw a graph and title it position time graph, label the x-axis as time (in 1 s increments up to 10), and the y-axis as position (in 10 meter increments up to 50). Describe one scenario this graph could show. Upcoming dates Friday, 8/28 – Student information sheet is due by 4:00 PM Wednesday, 9/2 – Quiz Tuesday, 9/8 (at 4:00) – last day to turn in missing work for unit 1 (this is a ‘A’ Day) Wednesday, 9/9 - Unit 1 test For additional quiz and test dates, see my webpage.

Graphing Instructions Title your graph – Position vs Time graph Label your Y-axis position (m) Label your X-axis time (s) Time should be in .5 s increments up to 15 s Distance should be in 1 meter increments up to 30 Plot the point for the fast ball data (use a colored pencil). Draw a best fit line and label the line fast ball. Plot the point for the slow ball data (use a different colored pencil). Draw a best fit line and label the line fast ball. Plot the point for the reverse ball data (use a different colored pencil). Draw a best fit line and label the line fast ball.

On the back of your graph respond to the question below 1. How did the slope (steepness) of the lines compare to each other? 2. Describe the direction of the ball during each of the three rolls. 3. What role do you think force and mass played in this experiment?

On the back of your graph respond to the question below 1. How did the slope (steepness) of the lines compare to each other? Visually the fast bowl, then reverse bowl, then slow bowl. The slope of line tells how fast the object is moving. Steeper = greater velocity. 2. Describe the direction of the ball during each of the three rolls. Considering the zero meter mark was the point of reference…the fast and slow bowl were moving away from the reference point. The reverse bowl was moving towards the reference point. 3. What role do you think force and mass played in this experiment? When I applied a greater force the ball went faster. If the mass of the ball increased then I would need to apply a greater force to keep the velocity of the ball the same.

Mass and Weight Mass is a measure of the number of atoms in an object combined with the density of those atoms. Mass is matter In order for mass to change the original object must be changed (chemical reaction, physical modification of its state). Weight is a function of mass and the effect of gravity. Weight can change based on the gravitational force. Example: my mass on earth and the moon are the same but I weigh less on the moon than on the earth.

Cool Down Explain the connection between distance, time, and speed.

Let’s take a walk

Vector v. Scalar Quantities Vector Quantity Fully described by both magnitude (number plus units) AND direction Represented by arrows -displacement -velocity -acceleration -force Scalar Quantity Fully described by magnitude alone -distance -mass -temperature -time -speed -electrical charge Intro idea with displacement v. distance demonstration. Pages 19-21 and 48-56

Speed and velocity video

How to approach problem solving in Physics Use a systematic way of analyzing a physical situation (aka a short story in Physics). We all use the same method of problem solving for the following reasons: We are all speaking a common language Repetition = retention (and leads to a deeper understanding) I can see the process that is going on in your mind…leading to partial credit!

GUESS Method Method for solving word problems Given: Unknown: relevant information clearly labeled symbol and units Unknown: Identify what the problem is asking you to solve for clearly labeled with symbol Equation: Write it using only symbols Substitution: Substitute given information into your equation Solve: Solve algebraically for your unknown term

Term Symbol/Variable Units Example Stem of Question Distance d m 5 m How far…? Displacement 3 m north How far (and what direction) from start…? Speed v m/s 27 m/s How fast…? Velocity (speed w/direction) -43 m/s How fast and what direction…? (direction can be shown with + or -) Acceleration a m/s2 -9.8 m/s2 -What is the change in velocity? -What is the acceleration? Time t s 7.3 s How long…? Initial speed or Initial velocity vi How fast is the object moving at first? Final speed or Final velocity vf How fast is the object moving at the end?

How do students feel about GUESS?

Applying GUESS to velocity Given distance and time solve for velocity.

Example: Sheldon from the ‘Bing Bang Theory’ runs 10 meters to the couch to play video games. It takes him 3 seconds to get there. Calculate Sheldon’s velocity.

Make your own problem with an Elbow partner and solve it. Write it on the back of your warm-up which is called the ‘cool down’

Finishing the day When you and your partner are done turn in your warm-up to the black tray.