HW

Next class, we will begin a new formal lab.  Hooray!

We will be comparing techniques for measuring speeds of motorized cars:

- photogate timer

An electronic timer with a light-gate - the timer records the amount of time for the object (car) to pass through the light beam.  The speed can be determined from that time and the width of the object.

- ticker tape timer

An electric timer that has paper tape pass through it.  It "clicks" 10 times per second and leaves a black dot on the paper tape.  The time between dots is 0.1 seconds.  By graphing the dots, the speed can be determined.

- stopwatch

Similar to what we just did in the informal lab.

Your task will be to compare the methods by percent different and try to judge which you think gives a more realistic picture of the car's speed.

Your homework - formulate a hypothesis:  Which method do you think is most accurate?  How will you know which is accurate?

homework

For next class:

Determine the average speeds associated with your data - for all of the objects, including yourself.

These values will likely be in m/s.

Show how to compute the values in miles per hour.  Describe how this conversion can be done.  Do not use an online conversion tool, unless it is to verify your results.

Also, find a good definition of "instantaneous velocity" by next class.

Hooray!

for Friday

Read about 2 of the following 3 technical devices:

microphones
telephone (the basics - the older voice box)
guitar pickups

Or look into something else cool that involved electromagnetic induction.

Yay!

topics for test

Electrostatics:

Coulomb's law
charge of electron / proton
inverse square law
electric field

Circuits:

current
voltage
resistance
power (recall light bulb problem)
series
parallel
combination circiuts

Magnetism

natural magnetism
electromagnetism
electromagnets
motors
right hand rule