Soaring Straws

Goals:

To collaboratively construct a straw rocket launcher.

To determine the relationship between gravitational and elastic potential energy.

Materials: scissors, rubber band, 3 plastic straws, meter stick, marker, metric ruler, toilet paper tube, masking tape, balance.

Procedure:Part 1-Constructing the rocket and launcher

Cut a rubber band and tape it across an open end of the toilet paper tube. The rubber band should be taut but not over stretched. This will become your launcher.

Cut 3cm off of one of the straws.

 Lay the 2 other straws side by side, separated by the 3cm piece. Be sure to line up all 3 ends of the straws evenly. Tape the straws together.

Starting from the untapped end, mark off 1cm increments on one of the long straws, using the marker and metric ruler. This will become your rocket.

Part 2: Launching practice

Use a balance to find the mass of the rocket in grams. Record your measurement.

Place the two long ends of your rocket through the tube (they should hang out of the bottom of the tube) so that the short end rests on the rubber band.

Practice launching your rocket by grasping the bottom straw lengths and gently pulling downward and releasing. Caution: Be sure to aim your rocket upwards and NOT toward a classmate! Repeat several trials until you are comfortable with the procedure.

Part 3: Calculations:

You will be recording two different measurements with your rocket launcher onto your data table:

  1. The amount of the stretch of your rubber band. This can be observed by recording the centimeter marks on the rocket base from the bottom of the launch tube.
  2. The height that your rocket travels. This can be observed by having a group member hold the meter stick at the zero mark directly above the top of your launcher.

Your group should launch your rocket using three (3) different amounts of stretch. Record the average height for each stretch trial. Each stretch level should include three (3) trials from which to obtain an average height.

Using the formula for Gravitational Potential Energy:

GPE=mgh

(where m=Mass of the rocket; g = 10m/s2; h=Height the rocket soared)

Calculate the GPE for each stretch amount.

Soaring Straws Data Table

Mass of the straw rocket:

Amount of stretch (cm) / Height- trial 1 (m) / Height- trial 2 (m) / Height- trial 3 (m) / Average height (m) / GPE

Reflection Questions

1)Which variable in your data table is the manipulated variable? Which was the responding variable? How do you know? (what variable did you change for each set of trials and which variable responded to those changes?)

2)In this lab, what measurement is related to the elastic potential energy?

3)Using a sheet of graph paper, make a graph of your results. Show GPE on the vertical axis and the amount of stretch on the horizontal axis. What conclusions can you make by interpreting the graph? (What is the relationship between GPE and EPE?)

4)When you release the rocket, what kind of energy does the rocket have just after takeoff? What are the GPE and EPE at this same point?

5)You measured the GPE of your rocket at its maximum height in each trial. What can you predict the kinetic energy of your rocket will be at takeoff?

Reflection Questions

6)Which variable in your data table is the manipulated variable? Which was the responding variable? How do you know? (what variable did you change for each set of trials and which variable responded to those changes?)

The amount of stretch of the rubber band was the manipulated variable. The height of the flight was the responding variable.

7)In this lab, what measurement is related to the elastic potential energy?

The change in the amount of the stretch is the elastic potential energy.

8)Using a sheet of graph paper, make a graph of your results. Show GPE on the vertical axis and the amount of stretch on the horizontal axis. What conclusions can you make by interpreting the graph? (What is the relationship between GPE and EPE?)

The longer the stretch of the rubber band (EPE) the higher the flight of the rocket (GPE). This is a direct relationship

9)When you release the rocket, what kind of energy does the rocket have just after takeoff? What are the GPE and EPE at this same point?

Kinetic energy. EPE is at max just before take off and GPE is zero. As the rocket flies, EPE is decreasing and GPE is increasing until the rocket reaches max height. Then GPE is max and EPE is zero.

10)You measured the GPE of your rocket at its maximum height in each trial. What can you predict the kinetic energy of your rocket will be at takeoff?

Kinetic energy would be max and then gravity takes over an slows the rocket down until it actually stops at the height of its flight.