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Elementary Science

Learn about the different forces that affect motion, including gravity, friction, and magnetic force. Discover how forces can cause objects to move, slow down, and stop.

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Elementary Science

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  1. Elementary Science Science Focus Lesson SC.5.P.13.1 Forces Polk County Public Schools

  2. SC. 5.P.13.1 Benchmark: Identify familiar forces that cause objects to move, such as pushes or pulls, including gravity acting on falling objects. Essential Question: How is the motion of an object affected by the forces acting upon the object? Vocabulary: force magnetic force gravity friction

  3. What is a force? • A force is a push or a pull. • Forces CHANGE motion • Forces cause objects to start moving, stop moving, change speed or direction.

  4. Gravity • Gravity is the force that attracts objects toward each other. • Gravity keeps Earth and planets in orbit around the sun • Gravity keeps the moon in orbit around the Earth • On Earth, gravity makes objects fall to the ground

  5. Gravity has unique characteristics • Gravity can act from a distance, it is NOT necessary for two objects to have contact with one another • Objects that have a greater mass produce a greater force of gravity • Objects that are closer to one another produce a greater force of gravity • All objects, regardless of mass, are pulled at the same rate of speed

  6. Friction • Friction is a force between two surfaces rubbing against each other. • Friction is a force that works against the motion of an object. • Friction allows your bicycle to STOP when you apply the brakes • Friction prevents your feet from slipping when you are walking

  7. Friction has unique characteristics • Friction works only through direct contact-surfaces must rub against one another • Friction takes place between any type of matter: solid, liquid, or gas • Rough surfaces produce more friction than smooth surfaces • The greater the force pushing surfaces together, the greater the friction

  8. Magnetic Force • Magnetic force occurs between a magnet and matter that contains iron (or a few other magnetic materials) • The area around a magnet where the force of magnetism can be felt is called a magnetic field

  9. Magnetic Force has unique characteristics • Magnetic force works at a distance • As the distance between a magnet and a magnetic object INCREASES the force of the magnetism DECREASES • All magnets have a north pole and a south pole • Opposite poles ATTRACT, or pull on, each other • Like poles REPEL, or push against, each other • Magnetism is strongest near the magnet’s poles

  10. Summarizing In your science notebook… 3- Name 3 forces 2- List 2 ways that a force can change motion 1- Define “ Force”

  11. Forces change motion • The motion of an object will change if it is pulled or pushed by something • Pulling or pushing applies a FORCE to an object • The amount of change in motion depends on the amount of force applied to it • The greater the force, the greater the change in motion

  12. Greater mass requires greater force • The mass of an object affects the amount of force that is needed to change the motion of an object • More force must be applied to change the motion of a 120 kg football player than a 100 kg football player

  13. Forces work together • Gravity, friction, and other forces combine to change an object’s motion • A bowling ball moves down the alley when you apply a strong force, as it moves friction between the ball and the alley’s surface slows the ball down • A baseball moves because of the strong force of a bat, as it moves friction between the ball and the air slows it down, as it moves gravity pulls it to the ground

  14. Air resistance is friction with air • As gravity pulls an object to the ground the air around it slows it down. • Air is matter; there is friction when objects move through it • The more surface area an object has the more air resistance it will experience. • Air resistance works against gravitational force to slow thing down as they fall.

  15. Summarizing Answer the following question in your science notebook: A baseball player hits a ball, it slows as it flies through the air, it lands on the ground, rolls into the outfield, and then stops. Explain what forces start the ball moving and cause the ball to slow down, fall down, and then stop.

  16. Guided Practice • 1. A circus acrobat was shot out of a cannon. As she flew across the room, she began to fall down toward the net. • What force caused the acrobat to fall down toward the net? • A. friction • B. heat • C. gravity • D. wind

  17. C is correct!!! • Gravity is the force that pulls objects to the Earth

  18. 2. A rolling ball will slow down until it finally stops. What force slows down and stops the ball? A. gravity B. solar power C. friction D. speed

  19. C is correct!!! • Friction is the force that slows objects down and causes them to eventually stop.

  20. 3. A soldier with a parachute jumped out of an airplane. After he opened his parachute, he fell more slowly. What upward force slowed down his fall? A. gravity B. magnetic force C. air resistance D. weight

  21. C is correct!!! • Air resistance slowed down the fall of the soldier to the ground. Air resistance is friction with the air and works against gravitational force.

  22. 4. Mike lifted a heavy box. What force did he have to overcome to move the box upward? A. gravity B. air resistance C. friction D. muscular

  23. A is correct!!! • Gravity is the force that pulls objects to the ground, but it is also the force that holds objects, and us, to the ground.

  24. Summarizing How is the motion of an object affected by the forces acting upon the object? Answer this question using the following words. friction gravity magnetic force push or pull force

  25. Check Your Understanding 1. William used a hammer to pound a nail into a wooden board. When the nail was about halfway through the board, he stopped and turned the board upside down. The nail stayed in place in the board. Which of the following acts on the nail to keep it in place in the board? A. Friction B. Gravity C. Magnetism D. Weight

  26. Check Your Understanding 2. Jamesha has a bar magnet. What will happen when she brings the north end of her magnet to the south end of Brittany’s magnet? A. They will attract B. Nothing will happen C. They will repel D. Sparks will fly

  27. Check Your Understanding 3. A 10 kg, 15 kg, and 20 kg rock are rolling down a hill. Which rock will require the most force to stop? • 10 kg rock • 15 kg rock • 20 kg rock • All 3 rocks will require the same force

  28. Check Your Understanding 4. The students in Mrs. Hoffman’s class played tug-of-war. The girls pulled in one direction with a force of 150 N. The boys pulled in the opposite direction with a force of 100 N. Who won the game and why did they win? • The boys won because they applied a stronger force to the rope • The boys and the girls tied because they applied equal forces to the rope • The girls won because they applied a stronger force to the rope • Too much force was applied, the rope broke

  29. Check Your Answers • A. Friction • A. They will attract • C. 20 kg rock • C The girls won

  30. Summary Question How do forces affect the motion of an object?

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