Speeding up is also called acceleration, and slowing down is deceleration. When speed increases, the object is accelerating. When speed decreases, the object is decelerating. For example, a car may go from a speed of zero miles per one hour to a speed of 30 miles per one hour. In this case we have accelerated from zero to 30 miles per hour. When we feel ourselves pushed into our seats in a car, that's the car working to accelerate us. When we strain against our seatbelts as the car brakes, that's the car working to DE-celerate us.

Constant velocity is when we neither speed up nor slow down. If something moves at the same speed in the same direction, we say it has a constant velocity. It is not accelerating or decelerating.

Try this activity:

Activity 1: In the Real World

Materials:

Glue
1 two-liter soda bottle
1 small cork
1 cap for soda bottle (with a plastic cap liner)
1 string to suspend cork in half-filled water bottle

Procedure:

1. Print this table.
2. Measure height of bottle.
3. Attach string to cork (maybe by paperclip).
4. Measure and cut the string so that length of the cork attached to string is about two times longer than the height of the bottle.
5. Fill the bottle with water (leave room for cork string assembly so that the water does not overflow).
6. Remove bottle cap liner.
7. Attach string to bottle cap with glue.
8. Replace cap liner (so it sandwiches string between cap and liner).
9. Give the cap/string liner assembly time to dry.
10. Push cork through bottle opening and twist cap tightly.

What you've built is an accelerometer. Take it for a walk and observe the cork's movement. Observe and record any movement of the cork when you are:

1. At rest, i.e. not moving at all
2. Speeding up slowly, i.e. go from not moving to walking gradually and smoothly
3. Speeding up fast, i.e. go from not moving to walking suddenly
4. Constant speed slow, i.e. walk slowly and steadily
5. Constant speed fast, i.e. walk quickly but steadily
6. Slowing down slowly, i.e. go from walking to not moving gradually and smoothly
7. Slowing down fast, i.e. stop suddenly from walking

Try each condition a few times, and record your observations in the table you printed out.

BBS questions:

1. What did you observe when you were walking at a constant slow speed? What about when you were walking at a constant fast speed?
2. Under which condition did you see the cork move the most?

Now, you're ready to do experiments in Whyville. Instead of accelerating and decelerating yourself, you will slide a disk in different places in Whyville and measure how long it takes for the disk to slide to a stop.

1. Read this page to find out where you can go to slide disks in Whyville. This page will also tell you how to get a disk, slide it, and time it.


2. After each trial, be sure you record your data by saying

   record disk stopped at tt seconds

   This means, if you clocked your disk coming to a complete stop at 5.2 seconds, you'll record this data by saying

   record disk stopped at 5.2 seconds

3. When you've done a few trials and feel like taking a break, come back to this notebook and use the Data tab at the top to view your data.


4. In the Data tab, you will find instructions for calculating the rate of deceleration for each line of data and contribute your findings to the Kinematic Attic's collaborative graph.


5. To check out the collaborative graph and see what it tells you about what's different between sliding disks in one place versus another in Whyville, you can either click directly on the graph on the wall or use the Graph tab in this notebook.

With some disk sliding experience under your belt, you're now ready for a rousing game of competitive shuffleboard Whyville-style. At the Shuffleboard Courts outside Kinematic Attic, you can play shuffleboard by yourself or with friends on a variety of courts, from ice to carpet.

Just like in real life, shuffleboard in Whyville is played by sliding disks. When you slide disks in your data collection activity all over Whyville, you define how fast you want to slide the disk. When you play shuffleboard, you'll define one more parameter: the direction of the disk. These two parameters, speed and direction, define an object's motion at any given time.

So, go disk sliding in as many places as possible, to get experience under your belt on all sorts of different surfaces. Then, when you're ready for the next step, visit the Shuffleboard Courts outside Kinematic Attic to put your disk sliding skills to the challenge.

Have fun!