# Hands-on science (no lab required).

PREDICT

Suppose you wanted to design a U-shaped ramp like Mat Hoffman's half-pipe. Your goal: Release your "biker"--a marble--from one side of the ramp, and have it roll as high as possible up the opposite side. Should you release the marble neat" the top or bottom of the ramp? Should the ramp's surface be rough or smooth?

YOU NEED

2 chairs * yardstick (or tape measure) * chalk * scissors * duct tape (30 cm, or 12 in.) * 1 foam-insulation tube (180 cm, or 6 ft), cut in half lengthwise * * 1 marble * pencil * paper * clear tape (180 cm. or 71 in.) * 6 strips P-Grade sandpaper (3 cm by 30 cm, or 1 in. by 12 in.) * graph paper

* See Teacher's Edition p. 3 for details.

PROCEDURE

1. Divide into groups of 3 to 4 students.

2. Position two chairs (back-to-back) 80 cm (31 in.) apart. Mark the position of each chair on the floor with chalk.

3. Using duct tape, fasten one end of the tube (rounded side) to the back of a chair. The top of the tube should measure 80 cm (31 in.) from the floor. Label this chair "A."

4. Tape the opposite end of the tube to the other chair. This end of the tube should measure 90 cm (35 in.) front the floor. Label this chair "B."

5. Have one student release the marble front the top of the tube at chair A.

6. Have another student use a finger to mark the marble's highest ascent on the opposite side of the ramp.

7. Measure front the floor to the marked spot on the ramp. Record this height as Trial 1

8. Repeat Steps 5 to 7 two more times for Trials 2 and 3.

9. Re-tape the top of the tube on chair A so that it is 90 cm (35 in.) above the floor. (Make sure the chairs haven't moved.) Repeat Steps 5 to 8.

10. Re-tape the top of the tube on chair A so it is 100 cm (40 in.) above the floor. Repeat Steps 5 to 8.

11. Remove the tube from the chairs. Use the cleat" tape to attach the sandpaper strips--rough side up--onto the ramp until the entire length is lined. Repeat Steps 3 to 10.

12. Make a bat" graph of your results, using an average of the three trials.

CONCLUSIONS

1. List the two variables. or characteristics in the experiment that changed.

2. Why is it important to perform three trials for each ramp height?

3. Which starting height gave the highest results with and without sandpaper? Explain.

4. How did the sandpaper affect the marble's highest ascent? Explain.

5. Which combination of variables would you choose to create a super ramp? Why?

Materials: The tubing is available at most hardware stores, or see www.lowes.com. (Item number 21415: 3/4" x 6' x 3/8" Polyethylene Thermal Insulation Tube) If cost prohibits buying more than one 6-ft. section of tubing, modify the experiment so that each group of students could take turns using the same ramp.

1. Ramp starting height and ramp lining (with or without sandpaper).

2. Three trials were conducted to obtain more reliable results.

3. For both ramps, the starting height of 100 cm gave the highest ending position. That's because gravitational potential energy increases with height.

4. By adding sandpaper to the ramp, the marble rolled to a lower ending height. Sandpaper is rough-it created more friction to slow the marble down.

5. You will most likely choose a ramp without sandpaper and with a starting height of 100 cm.