EXPERIMENT 7.2

NEWTON'S FIRST LAW

Student Information:

PURPOSE:

To observe Newton's first law of motion through hands-on experiments.

MATERIALS:

SAFETY:

  • Always wear eye protection when conducting experiments.
  • Be careful when handling raw eggs to avoid contamination.
  • Clean up any broken eggs or spills immediately.
  • Use caution when cutting the aluminum pie pan with scissors.

BACKGROUND:

Sometimes it's hard to understand Newton's first law because it goes against our everyday experience (how can an object keep moving unless acted on by a force, for example). Experiments such as these help you visualize that this law of motion is really true.

Newton's First Law of Motion states that an object at rest will stay at rest, and an object in motion will stay in motion with the same speed and direction, unless acted upon by an unbalanced force.

This law is also known as the Law of Inertia. Inertia is the resistance of an object to any change in its state of motion. The more mass an object has, the greater its inertia and the more force required to change its motion.

Diagram showing marble paths in a pie pan

FIGURE 7.19 - Possible paths of a marble exiting a pie pan

QUESTIONS:

How can Newton's laws be observed?

HYPOTHESES:

1. Write your prediction of what will happen to a coin when a card is quickly removed from under it:

Write your prediction of what will happen when the card is removed slowly:

2. Write your prediction of what will happen when you stop a spinning hard-boiled egg:

Write your prediction of what will happen when you stop a spinning raw egg:

3. Write your prediction of what path (a, b, or c) the circling marble will take when it exits the pie pan in Figure 7.19:

PROCEDURE—PART 1:

  1. Place the small beaker or glass on the table, right side up.

  2. Place the index card on top of the glass so that it covers the opening. Center the index card so that the center of the card is over the center of the glass.

  3. Place the coin on the center of the index card.

  4. Flick the card quickly with your fingers so that it moves forward, uncovering the glass. You want to flick the edge of the card from the side. Don't flick upwards or downwards. Record what happens to the coin.

  5. Set up the experiment again. This time, instead of flicking the card, grasp the card with your fingers and slowly pull it away from the glass. Keep the card level as you pull it away. Record what happens to the coin this time.

PROCEDURE—PART 2:

  1. Place the hard-boiled egg on the table. Make sure it is on its side and not an end.

  2. Spin the egg and watch how it spins. Be sure it spins on its side. Record your observations.

  3. Do the same thing with the raw egg. Record your observations, noting the difference in the way the eggs spin, if any.

  4. Spin the hard-boiled egg again. Once it is spinning, reach down and stop it for an instant, then immediately let it go. Record what happens.

  5. Do the same thing with the raw egg. Record what happens in this case.

PROCEDURE—PART 3:

  1. Use the scissors to cut a quarter of the pie pan away. Examine the diagram in Figure 7.19.

  2. In this experiment, you are going to roll the marble into the pie pan as shown in Figure 7.19. The marble will roll around the pan, guided by the pan's walls. When it hits the edge where the quarter was cut out, it will begin to roll on its own.

  3. Before you actually do this, make sure you have written your hypothesis or your prediction of which path the ball will roll once it begins to roll on its own. There are three possible choices.

  4. Now you should actually perform the experiment. Hold the pie pan in place with one of your hands so that it doesn't move.

  5. Using your other hand, propel the marble straight into the pan so that it rolls around the side of the pan as shown in the figure. Watch which way it exits when it ends up moving. Record your observations.

VIDEO DEMONSTRATION:

Watch this video demonstration of Newton's First Law experiments:

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What to Look For:

  • Objects at rest staying at rest until acted upon by a force
  • Objects in motion continuing in motion unless acted upon by a force
  • Examples of inertia in everyday situations
  • How friction and other forces affect motion

CONCLUSIONS:

Explain what happened to the coin, the eggs, and the marble in terms of Newton's first law of motion. Use the terms, inertia, force, and friction in your paragraph. Make connections to what you've read in the text.

ANALYSIS QUESTIONS:

1. In Part 1, why did the coin fall straight down when the card was flicked quickly but moved with the card when pulled slowly?

2. In Part 2, why did the hard-boiled egg and raw egg behave differently when stopped briefly and released?

3. In Part 3, explain why the marble followed the path it did when exiting the pie pan.

4. How does friction affect each of the three experiments?

5. Give three examples from everyday life where Newton's First Law can be observed.

EXTENSION ACTIVITIES:

Try these additional activities to further explore Newton's First Law:

  1. Place a small object on a piece of paper. Pull the paper quickly. What happens to the object? Now try pulling the paper slowly. How does this relate to Newton's First Law?
  2. Research and design your own demonstration of Newton's First Law using household items.
  3. Investigate how seat belts in cars relate to Newton's First Law of Motion.

SUBMIT YOUR RESULTS:

Click the button below to submit your experiment results to your teacher.