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What is a Force

What is a Force

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What is a Force

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  1. What is a Force Chapter 1, Sec.2

  2. Force is measured in newtons (N)

  3. All forces are exerted by one object on another

  4. Forces don’t always equal motion

  5. Net Force • Combining all the forces exerted on an object

  6. Forces in the same direction • Add forces together • 25N + 20N = 45N

  7. Forces in different directions • Subtract forces • 12N – 10N = 2N

  8. Unbalanced Forces • Net force is not zero • Produce a change in motion • Necessary to cause stationary objects to move

  9. Necessary to change the motion of moving objects • Object continues to move when force is removed

  10. Balanced Forces • Net force is zero • Do not produce a change in motion • Do not cause a stationary object to start moving

  11. Main forces on an object • Gravity • Normal • Friction • Push/Pull • Tension

  12. Gravity • Keeps objects on the ground or attracted to the ground

  13. Normal Force • Prevents object from “falling into” whatever it is sitting on • Always perpendicular

  14. Friction • Opposes motion • Points away from direction of movement

  15. Push/Pull • Physical push or pull • Pushing a crate • Pulling a wagon • Wind moving a ship

  16. Tension • Results from a pulling force • Dragging something with a rope

  17. The child next door wants to take his German Shepherd (named Spot) for a ride on his wagon. He chases Spot (who is running away) while dragging his wagon behind him. What forces are acting on the wagon?

  18. Spot, the German Shepherd, is being walked by his best pal, Dot, the Siamese cat. Actually, Dot is pulling Spot across the ice rink, and disturbing the neighborhood hockey game. What are the forces acting on Spot?

  19. A girl is suspended motionless from a bar which hangs from the ceiling by two ropes. Diagram the forces acting on the girl.(hint: the bar is “part of” the girl)

  20. Answer

  21. An egg is free-falling from a nest in a tree. Neglect air resistance. Diagram the forces acting on the egg as it falls.

  22. Answer

  23. A rightward force is applied to a book in order to move it across a desk. Consider frictional forces. Diagram the forces acting on the book.

  24. Answer

  25. A skydiver is descending with a constant velocity. Consider air resistance. Diagram the forces acting upon the skydiver.

  26. Answer

  27. A force is applied to the right to drag a sled across loosely-packed snow. Diagram the forces acting upon the sled.

  28. Answer

  29. A car is coasting to the right and slowing down. Diagram the forces acting upon the car.

  30. Answer