# Fast and Easy Science Fair Projects: Up to Speed

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Plastic soda bottle (2-liter and clear)
Water
Food coloring
Pen
Tape Measure

Acceleration in a bottle

Purpose: To show changes in rate of speed.

Overview: Acceleration is an increase in speed. Physicists define it as a measure of rate of change of velocity over time. To accelerate means to go faster; to decelerate is to slow down.

Hypothesis: It's possible to prove that speed and acceleration are different and measurable by constructing an "accelerometer."

You need:

• 2-liter clear plastic soda bottle
• water
• food coloring
• pen or marker
• tape measure
• an adult with a car

Procedure: Partially fill a 2-liter clear plastic soda bottle with water. Add some food coloring so that you will be able to see the water's movement better. Screw the cap on tightly. Place masking tape along one side of the bottle's circumference. Draw a scale on it (millimeters or 1/4-inch increments).

Ask an adult with an automated-shift car to take you for a short drive. (Manual-shift cars could be jerky and uneven during acceleration.) Open the car's glove compartment and use the door as a shelf. Lay your "accelerometer" on it. Fix it there with masking tape or rubber bands. On the tape, mark the water level when the cat is not in motion.

When you are ready (remember to fasten your seat belt), have the driver accelerate. Observe how far up the scale the water moves. The faster the car accelerates, the steeper the slope of the water up the side of the bottle. The amount of water in the bottle has remained Constant, but the acceleration had Varied.

Next, have the driver hold a steady speed, like 40 Miles or kilometers per hour, on a highway. Is the water level at the same mark as it was when the car was at rest? Even though a car is travelling at quite a good speed, the acceleration is zero.

Results and Conclusion: Write down the results of your experiment. Come to a conclusion as to whether of not your hypotheses was correct.

Something more: What about deceleration, when the car is slowing down and coming to stop. Can your accelerometer also be used to compare rates of deceleration?