Park Physics with Sean Lally - 2017-2018

Read my earlier notes on gravitational acceleration.  Some of it may be confusing, but try your best. Then try these: 1.  A ball is dropped from rest and falls with no air resistance. A.  How fast is it traveling after 2,5 seconds, assuming that it hits nothing? B.  How far will it have fallen in this time? 2.  What does it mean to be weightless?  Give an example as well. 3.  Challenge question.  A rock is dropped from a bridge above a river and lands 1.5 seconds later?  How far above the river is the bridge?

Today we discuss the acceleration due to gravity - technically, "local gravity". It has a symbol (g), and it is approximately equal to 9.8 m/s/s, near the surface of the Earth. At higher altitudes, it becomes lower - a related phenomenon is that the air pressure becomes less (since the air molecules are less tightly constrained), and it becomes harder to breathe at higher altitudes (unless you're used to it). Also, the boiling point of water becomes lower - if you've ever read the "high altitude" directions for cooking Mac n Cheese, you might remember that you have to cook the noodles longer (since the temperature of the boiling water is lower). g = 9.8 m/s/s (approximately, near the surface of the Earth) Recall: https://www.youtube.com/watch?v=E43-CfukEgs On the Moon, which is a smaller body (1/4 Earth radius, 1/81 Earth mass), the acceleration at the Moon's surface is roughly 1/6 of a g (or around 1.7 m/s/s). On Jupiter, which is substan

https://www.youtube.com/watch?v=E43-CfukEgs Brian Cox in Cleveland https://www.youtube.com/watch?v=LWGJA9i18Co OK GO video

I will not collect this, but WILL check to see that you have completed (or at least attempted) it at the beginning of class. During class, you took some data - distance and time - for a falling ball.  Your purpose is to calculate the acceleration of the ball. We rearranged an equation in class to solve for acceleration.  This equation now looks like this: a = 2d/t^2 (Note that t^2 means t-squared.) Using the data your group took in class, calculate the acceleration for your ball.  You can first determine the average time to fall, as long as you kept the distance the same for each trial. Questions to answer after you calculate a: 1.  Should everyone in class have the same acceleration (approximately)? 2.  What causes the ball to accelerate? 3.  What are sources of error (or threats to validity) in this little experiment? 4.  What might be a better way (or ways) to perform this experiment? Thanks!

A runner stars from rest and accelerates at 0.5 m/s/s for 10 seconds. If using the equations of motion is still tricky for you, be sure to set up the 4-step process: - What is known? - What are you looking for? - What is a relevant equation? - Solve it. 1.  What is her velocity after 10 seconds? 2.  How far does she go in this time? 3.  What would a graph of her distance vs. time look like?  Draw a rough approximation. 4.  What would a graph of her speed vs. time resemble?  Draw a rough approximation. Here is a reminder from today's class:

The final equations are here:

If you haven't had a chance to play with Logger Pro or the graphing program of your choice, please do that ASAP.  Then read the material below, most of which is review from class. Intro to the mathematics of motion Today, we are going to talk about how we think about speed and the rate of change in speed (usually called acceleration).  It is a bit math-y, but don't panic - we'll summarize things nicely in a couple of simple-to-use equations. First, let's look at some definitions. Average (or constant) velocity, v v = d / t That is, distance divided by time.  The SI units are meters per second (m/s). * Strictly speaking, we are talking about speed, unless the distance is a straight-line and the direction is also specified (in which case "velocity" is the appropriate word).  However, we'll often use the words speed and velocity interchangeably if the motion is all in one direction (1D). Some velocities to ponder.... Approxima

Please use Logger Pro - link sent in email - or another graphing program. 1.  Distance (y axis) vs time (x axis): t (s)   d (m) 1        0.5 2.       2 3.       4.5 4.       8 5.       12.5 6.       19 If you use Logger Pro, please try to do the following: Label the columns with names and units. Autoscale so that the graph fits the space well. Try to fit a curve using the curve fit option under Analyze. 2.  Graph this data and apply a linear fit (with slope).  Try to determine the equation of this line: t (s)     d (m) 1.      5 2.      8 3.      11 4.       14 5.       17 6.        20 7.        23

Physics – Graphing Homework Please work on this in your notebook – it will not be collected. 1.  Graph the following data as a distance/position (y-axis) vs. time (x-axis) graph.  This is data that represents the motion of a toy car moving in a straight line.  Use any computer program you wish to use (Excel, Google, etc.): t(s)                   d(m) 0                      1.5 0.5                   1.8 1.0                   2.1 1.5                   2.4 2.0                   2.7 2.5                   3.1 3.0                   3.3 3.5                   3.5 4.0                   3.9 What can you say about the motion of this toy car? Have the computer determine the slope of the line. What does the slope represent? 2.  Now graph this set of data for a different vehicle: t(s)                   d(m) 0                      0 1                      2 2                      8 3                      18 4                      32

Woo Hoo – it’s physics problems and questions! OH YEAH!! Please complete these by next Monday, to be submitted for a homework grade.  1.  Determine the average speed of your own trip to school: in miles per hour. Use GoogleMaps or something similar to get the distance, and recall the time from your last trip.  Your answer should be in either miles per hour or kilometers per hour. 2.  What was the meter standard originally based on?  What is it now based on?  Why was a change ever made? 3.  What is the meaning of instantaneous velocity?  How can we measure it? 4.  Give a simple way to remember how fast light is. 5.  If you were to draw a graph of distance (y-axis) vs. time (x-axis) for an object moving at a constant speed, what would it resemble?  Draw or describe.  Now, if the object were accelerating (getting faster each second), what would the graph resemble?  Draw or describe.