EXPERIMENT 6.1

PURPOSE:

To observe how direction plays a role when objects are moving at different speeds.

MATERIALS:

• At least 4 eggs
• Two pieces of reasonably strong cardboard (like the cardboard found on the back of writing tablets)
• Several books
• A pair of scissors
• Ruler
• A large tray or cookie sheet
• Paper towels
• Kitchen table
• Eye protection such as goggles or safety glasses

BACKGROUND:

The difference between speed and velocity is very important in physics. This experiment demonstrates that fact.

QUESTION:

How does direction affect two objects relative to each other when they are moving in the same direction with the same speed? What about when they are moving with the same speed in opposite directions, towards each other?

HYPOTHESIS:

Write what you predict will happen to 2 eggs that roll down a ramp in the same direction. Write what you predict will happen to 2 eggs that roll down ramps in opposite directions, towards each other.

PROCEDURE:

1. This is a potentially messy experiment, so put some paper towels on the table for easier clean-up.
2. Make a pile of books about 8 inches high on the tabletop. (You will need to make a second pile 8 inches high for step 7, so gather all books now.)
3. Take the cardboard pieces and measure 2 inches in from each side and 1 inch from the top. Cut the 2 in × 1 in rectangles out (see Figure 6.12). Fold the long edges up to form "railings" on each side. Fold the short edge back.
4. Next, tuck the short edge between the top 2 books so that the cardboard leans against the pile of books, making what looks like a slide going from the top of the books to the tray. Your set-up should look like Figure 6.13.
5. Trial 1—Hold two eggs together on top of the slide. Hold them so that one egg is behind the other. Release them together, allowing them to roll down the slide one behind the other. Use your other hand to stop them when they roll off the slide and onto the tray. Note whether the eggs have been damaged or not. Record your observations in your data table. If the eggs were damaged, get new ones. If not, you can reuse them.
6. Trial 2—Lay one egg on the tray at the bottom of the slide. Allow the other egg to roll down the slide and hit the egg at the bottom of the slide. Record your observations, noting any damage caused. Once again reuse any undamaged eggs.
7. Build another slide like the one you've been using. It needs to be close to the same height as the first slide.
8. Place the two slides so that they are on opposite sides of the tray and so that they meet in the center of the tray.
9. Trial 3—Place one egg at the top of one slide and the second egg at the top of the other slide.
10. Simultaneously let both eggs go, allowing them to roll down the slides and crash into each other. Record your observations, noting the damage to the eggs.
11. Clean up and put everything away.

Figure 6.12: Cardboard Setup

Cardboard setup with dimensions and fold lines.

Figure 6.13: Experimental Setup

Experimental setup with books and cardboard ramp.

ANALYSIS QUESTIONS:

INTERACTIVE SIMULATION:

Watch this video demonstration of the experiment:

CONCLUSION:

Based on your observations and analysis, explain how this experiment demonstrates the importance of direction in velocity. How does this relate to real-world situations involving moving objects?