TO THE STUDENT

Welcome to this experimental science test. We hope that you will find it interesting and worthwhile. Carefully read through these directions and the directions on the next page before you begin to work.

You may be part of a group for the first part of this exercise. Each group should carry out the experiment and collect the data together, but each student must record the data in his or her own booklet. Be sure to record the data exactly as you observe them. After the data has been collected, each student should answer the questions independently.

After you have finished your experiment and have recorded all of the data, you will be asked to answer some questions about the experiment and the data you recorded. Your answers must be written in this test booklet in the space provided. Make sure that you understand each question before you begin to write. At any time while you are writing your answers, you may look back to the directions for the experiment and the data you collected. Be sure that your answers are written as clearly and neatly as possible.

Before you turn the page, read the list of materials given below and check to make sure that your group has everything listed.

You have noticed that your body gets pushed against the side of a car (or bus) when the vehicle makes turns. You want to figure out why this happens. You have learned in science class that objects moving in a straight line continue moving n a straight line unless acted on by an outside force. This is known as Newton's First Law, or the law of inertia. We are going to look at objects that move in circles to see what keeps them moving in a circle. You will then use this knowledge to figure out why you get pushed against the side of the car or into the person sitting next to you when the car turns a corner.

You will work in a group to perform the experiments, but each student will record his or her own observations and answer the questions alone.

1. You are going to roll a marble on a flat surface (a table top or the floor). You will place the marble in the groove that runs down the ruler so that you can direct the motion of the marble. To start the marble in motion, slightly elevate the ruler with the marble in the groove. Note the path that the marble takes. Record your observations on the observation sheet.

2. Place the plastic plate on a flat surface. Using the groove of the ruler to start the marble in motion, roll the marble around the edge of the plastic plate (see Figure 1 below). Observe the motion of the marble and record it on the observation sheet.
   

3. Cut the plastic plate in half. Roll the marble around the half-plate (see Figure 2 below). Record your observations.

1. The marble rolling off the ruler onto the floor or table top: ____________________________________________________________________________________

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2. The marble rolling around the edge of the plastic plate: ____________________________________________________________________________________

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3. The marble rolling around the edge of the half-plate: ____________________________________________________________________________________

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4. The marble rolling around the edges of the two half-plates: ____________________________________________________________________________________

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During this activity, you will work with a partner, but each student will record his or her own data.

• Place the tennis ball inside the plastic bag.
• Use one end of your string to tie your plastic bag shut. Make sure you have enough string left over to use as a handle. Also, double-check the strength of your knot.

Once you have completed the above assembly you will go outside for five minutes. Your pair will play a game of catch using the ball-in-the-bag device you have made, as shown in Figure 4.

• You and a partner should stand 4-5 meters apart.
• Holding your device by the string, swing the ball around your head in a circle.
• Determine when to let go of the string so that the ball will go to your partner.
• Continue to play catch until you have determined the proper "letting go" point.
• Give the ball-in-the-bag device to your partner, so that your partner can determine the proper "letting go" point.
• Go back to your classroom and complete the following questions on your own.

Please answer the following questions by yourself.

1. Explain your location, your partner's location, and the "let go" point for your game of catch. Why must you let go at that point?

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2. Suppose that the plate were cut as shown below in Figure 5 instead of being cut in half. Draw the path that the marble would take if it were rolled around the edge. Explain your drawing.
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3. If you are traveling in a vehicle that makes a sudden turn, your body gets pushed against the side or door. Explain why that happens. You are encouraged to use diagrams to help answer the question.

    

    

    

    

    

    

    

    

    

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