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Investigating Motion

Investigating Motion. Science Chapter B2. Text Pages B43-B73. Lesson 2. What Affects Motion?. Text Pages B49-B53. Vocabulary. inertia:. the tendency of an object to stay at rest or to remain in motion unless an outside force causes a change. Inertia.

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Investigating Motion

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  1. Investigating Motion Science Chapter B2 Text Pages B43-B73

  2. Lesson 2 What Affects Motion? Text Pages B49-B53

  3. Vocabulary inertia: the tendency of an object to stay at rest or to remain in motion unless an outside force causes a change

  4. Inertia • An object that is moving will stay moving until something makes it stop. • A baseball flying through the air • A marble rolling across the floor • An object that is sitting still will stay sitting still until something makes it move. • A marker sitting on a table • A soccer ball sitting on the field • Every object has inertia!

  5. Inertia • A force is needed to overcome inertia. • A push or a pull • What forces could overcome the inertia of the following items? • A baseball flying through the air • A marble rolling across the floor • A marker sitting on a table • A soccer ball sitting on the field

  6. Inertia and Vehicles • When we travel in a vehicle, we feel inertia. • Our bodies seem to move backward when a vehicle takes off suddenly. • Inertia tries to keep them in the same place. • Our bodies keep moving forward when a vehicle stops suddenly. • Inertia tries to keep them moving forward.

  7. Seat Belts Save Lives! • A seat belt is a force that can overcome inertia. • Seat belts keep our bodies from moving forward when a vehicle stops suddenly.

  8. Inertia and Bicycles • Inertia must be overcome when we ride a bicycle. • A force is needed to make the bicycle go. • We push on the pedals to make the bicycle start moving. • A force is needed to make the bicycle stop. • We apply the brakes to make the bicycle stop moving.

  9. Invisible Forces • Some forces cannot be seen. • Air molecules bump against moving object and slow them down. • Gravity pulls objects toward the earth. • Friction works against the movement of objects.

  10. Missing Forces! • In outer space, there are no air molecules to push against moving objects. • When spacecraft get far from the surface of the earth, Earth’s gravity is too week to overcome their gravity. • Once a spacecraft gets moving, it can keep going because there is nothing to stop it.

  11. Pairs of Forces • Forces always work in pairs. • One force pushes in one direction while another pushes with equal strength in the opposite direction. • One force is called the action force. • The other force is called the reaction force.

  12. Pairs of Forces • A jumping frog is a good example of pairs of forces. • When the frog hops forward, the lily pad moves backward. • Which is the action force, and which is the reaction force?

  13. The Earth vs. You • We experience action and reaction forces when we walk. • When we take a step, we push against the earth in order to move forward. • This is the action force. • We don’t feel it, but the earth also pushes against our feet when we walk. • This is the reaction force. • Why doesn’t the earth move like the lily pad?

  14. Put it all together! • How does inertia affect an object’s motion? • Name some forces that affect motion. • How do forces work?

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