How do science concepts apply to your world? Here are some questions you'll be able to answer after you read this chapter.

• How can two people look at the same object, and only one of them see the object as moving?
• One person says that your school is 5 blocks from the library, and another person says the two buildings are 7 blocks apart. How can both people be right?
• What does a car's speedometer measure?
• When you drop a stone off a cliff, how fast does the stone fall?
• How can something that is slowing down be accelerating?
• How do ships stay on course?

How Does a Ramp Affect a Rolling Marble?

Procedure

1. Form a ramp by placing one end of a 1-meter-long board on a stack of six identical books.
2. Have your partner release a marble at the top of the ramp. Use a stopwatch to measure the time the marble takes to reach the bottom. Record this time.
3. Predicting   How many books tall would the stack have to be to double the time needed for the marble to reach the ramp's bottom? Record your prediction.
4. Test your prediction. Remove one book from the stack and repeat Step 2. Continue this process until the time needed for the marble to roll down the ramp doubles.

Think About It

1. Predicting   What would happen to the time needed for the marble to roll down the ramp if the ramp were nearly horizontal?
2. Formulating Hypotheses   If you keep adding books to the stack, will the time needed for the marble to roll down the ramp decrease indefinitely? Explain your answer.