Newtons First Law Vocabulary Inertia Newtons First Law

Newton’s First Law Vocabulary • Inertia • Newton’s First Law “Campbell’s Soup” (1968) Andy Warhol This topic can be found in your textbook on pp. 125 -129.

Think about it… § Imagine a stationary object. Here’s some help: What would it take to get the stationary object to move? It would take someone applying an unbalanced force.

…ti t § Or, think about an object in motion. . . What does it take to stop it?

Think about it… §An unbalanced force can start motion. §An unbalanced force can stop motion.

But what if the forces are balanced? §Then the object will continue its current motion.

Inertia §The tendency of a body to maintain its state of rest or uniform motion unless acted upon by an unbalanced external force.

Watch this: Click here to watch the video

Inertia § The property of inertia is SOLELY dependent on mass. More mass = more inertia.

Watch this Click here to watch video. Why was the smaller plane more maneuverable?

Take a look Click here to watch video.

What were the balanced forces that kept the tomato stationary? Force of friction to right. Force of sword to left. Forces are balanced so tomato stays at rest.

Take a look Click here to watch video.

No forces sideways! What forces are acting on the cheetah? The cheetah in motion stays in the same motion until it exerts an unbalanced force to change its direction.

Galileo’s Thought Experiment on Inertia

So let’s look at objects in motion: Click here to watch video.

Newton’s 1 st Law §Isaac Newton performed scientific experiments which confirmed Galileo’s thought experiments, and the Law of Inertia became known as Newton’s First Law of Motion: §An object at rest will stay at rest and an object in motion will stay in motion unless acted upon by an unbalanced outside force.

Your turn § Write down 5 examples from the following video that demonstrate inertia. Be sure to state the object you’re observing, its initial motion, the action, and the resulting motion.

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Try these: 1. Imagine a place in the cosmos far from all gravitational and frictional influences. Suppose that Cosmo Naught visits that place and throws a rock. What will the rock do after you release it? a. gradually stop. b. continue in motion in the same direction at constant speed. Why? ? ?

2. Bob Bowles throws a 6 -kg bowling ball that moves horizontally with a speed of 4 m/s. How much net force is required to keep the ball moving at this speed and in this direction?

3. Mel Lowe is standing in on his speed boat. The boat suddenly accelerates. Describe Mel’s motion relative to a) the water b) the boat

4 a) An object has only one force acting on it. §Can it be at rest? §Can it have acceleration? b) A different object has zero acceleration. §Does this mean that no forces act on it?

5. Stan Still spends most Sunday afternoons at rest on the sofa, watching pro football games, and consuming large quantities of food. What effect (if any) does this practice have upon his inertia? Explain.

6. Ima Wilde is being chased through the woods by a bull moose that she was attempting to photograph. The moose can run faster than Ima. What strategy can she use related to Newton’s 1 st Law to get away from the Moose? Explain.

7. Two bricks are resting on edge of a shelf. Tu Short stands on her toes and spots the two bricks. She acquires an intense desire to know which of the two bricks is most massive. Since Tu is vertically challenged, she is unable to reach high enough and lift the bricks; she can however reach high enough to give the bricks a push. Discuss how the process of pushing the bricks will allow Tu to determine which of the two bricks is most massive. What difference will Tu observe and how can this observation lead to the necessary conclusion?

Newton’s First Law Summary § An object at rest will remain at rest and an object in motion will remain in motion unless acted upon by an unbalanced external force.