Straight Line Motion in Two Parts

Ann M. W. Brandon Joliet West High School
401 N. Larkin Ave
Joliet IL 60435
(815) 727-6950

Objectives:

Students will observe both constant and accelerated (changing) motion.
They should be able to calculate speed from distance and time measurements.
They will graph distance vs time for each motion and observe that the two
motions look different when graphed. This was designed for upper middle school

Materials Needed:

Per group of 2 or 3 students:
Stomper (battery powered toy car)
Stopwatch, or second hand on a clock
Meter Stick
Toy car, not powered
A long slope (a table with two legs propped up with some books)

Strategy:

Part I: Stomper

Issue a Stomper, stopwatch, and meter stick to each lab group.

Ask the following questions, in writing:
Describe the motion of the car as it rolls along the table.
How can you tell what it is doing?
What do you need to know to find the speed of your Stomper?
Find the average speed of your stomper over a distance of 1 meter.
What can you measure? How many trials should you try?

Is this a constant speed? How can you tell?
Find the average speed for 2 meters.
Was it the same as the average speed for 1 meter?

Graph the Distance Traveled vs the Time Taken for 1, 2 and 3 meters.
Describe this graph.
Is it straight?
Is this constant motion or changing motion?
What is the relationship between the Distance Traveled and the Time Taken?
Look at the slope (rise over run) of the graph, and calculate this slope.
What does this tell you?

Part II: Car Rolling Down Hill

Trade the toy car for the Stomper.

Start your car at the top of the hill.
Describe its motion.
Is it constant motion? Or is it accelerated (changing) motion?

Find the average speed of your car for 1/2 meter.

Repeat for 1 and 1 1/2 meters (or the end of the hill)
What do these speeds tell you? Is it constant motion, or accelerated
motion?

Graph the Distance Traveled vs the Time Taken.
Describe this graph. Is this a straight line?
What does this graph tell you about the motion of the car rolling down the
hill?

Performance Assessment:

1. Use a "Two Speed" Friction powered car. Wind it up and let it go.
Ask for descriptions of its motion. Then ask for a sketch of a distance vs
time. It will have a section of constant motion, then shift gears, accelerate,
and have a new, faster constant motion.
2. Draw a graph of some motion, and ask for a description of that
motion.

Conclusions:

Students should be able to measure distance and time.
They should be able to combine them to find speed.
They should be able to graph distance vs time, and find the slope to find
the speed.
They should recognize the difference between constant motion and
accelerated motion.
They may even be able to tell the difference in the motions by the sound of
the cars as they roll along.