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Study Guide for Force And Motion Unit Test

Study Guide for Force And Motion Unit Test. Chapter 1 Section 1. Motion- the state in which the distance between two objects is changing Reference point- a place or object used for comparison to determine if something is in motion.

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Study Guide for Force And Motion Unit Test

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  1. Study Guide for Force And Motion Unit Test

  2. Chapter 1 Section 1 • Motion- the state in which the distance between two objects is changing • Reference point- a place or object used for comparison to determine if something is in motion. • Speed – the distance an object travels in one unit of time ( S= D/T) • Average speed- Total distance divided by total time • Velocity-Speed in a given direction (4 m/s EAST)

  3. Using the Speed Formula How long does it take a bird to fly 300km if it travels at a speed of 50 km/hr? T= D/S = 300 km/50 km/hr = 6 hr Jimmy can pitch a baseball a distance of 48 meters in 1.5 seconds. How fast is his pitch? S= D/T = 48 m/1.5 s = 32 m/s

  4. Graphing Speed • The following is a data table showing the distance a jet travels in a certain amount of time from Denver to Phoenix. Be able create a graph from a data table.

  5. Graphing Speed

  6. Be able to analyze a graph…

  7. ????

  8. Chapter 1 Section 3 • Acceleration- the rate at which velocity changes • Acceleration= final velocity- initial velocity ÷ time • Units… m/s²

  9. A skydiver accelerates from 20 m/s to 40 m/s in two seconds. What is the skydiver’s acceleration? • A= f.v.-i.v./time= 40-20/2 = 20/2= 10 m/s²

  10. Three ways an object can accelerate…

  11. Graphing Acceleration (note- y-axis)

  12. Differences between speed and acceleration graphs… • What is on the y-axis • Horizontal line means something different

  13. Chapter 2 Section 1 • Force- a push or a pull • Balanced force- equal forces acting on one object in opposite directions/ doesn’t change the object’s motion • Unbalanced force- can cause an object to start moving, stop moving or change direction/ changes an object’s motion • Net force- the overall force on an object after all the forces are added together • Mass- amount of matter in an object • Inertia- when an object tries to resist its change in motion

  14. Newton’s First Law • An object at rest stays at rest. • An object in motion will remain in motion unless acted upon by an unbalanced force. • A ball won’t start to move unless it is kicked or thrown. • That ball won’t move through the air forever. Air resistance, friction from the ground, a person’s hand are all unbalanced forces.

  15. Chapter 2 Section 2 • Newton’s Second Law • Force = Mass x Acceleration • Mass units– kg • Acceleration units – m/s² • Force units- Newtons

  16. W = m x gravity constant • Find the weight of a 30 kg object on the earth.  •  W   =  m x g •   W  =  30 kg x 9.8 m/sec2 • Weight on the earth  = 294 Newtons

  17. Chapter 2 Section 3 Friction • Friction is a force that one surface exerts on another when two objects rub against each other • Examples– Skateboarder puts his/her foot down on the ground to slow down -- A baseball player slides into home base

  18. The factors that determine how much friction there will be between two objects are… • The types of surfaces involved • How hard those surfaces push together.

  19. Friction opposes motion

  20. Examples of friction

  21. Friction examples… • Friction is reduced when… Speed skater/luge moves across the ice smoothly Adding oil to hinges • Friction is increased when… A car has new tires A boot has thick treads

  22. Air Resistance • A type of fluid friction that occurs when objects fall through the air • This slows down the speed of objects falling. It opposes motion so goes in the opposite direction of gravity and motion.

  23. Gravity • Gravity is a force that pulls objects towards Earth. • Free fall occurs when it is the only force acting on a falling object. • Terminal velocity is the greatest velocity an object reaches.

  24. How does weight relate to Newton’s second law? • Weight is defined as the force of gravity on a person or object. • You can rewrite Newton’s Second Law of motion (Force = mass x acceleration) as… • Weight = mass x gravity (9.8 m/s²)

  25. Strength of Gravity • The two factors that determine the strength of gravity between two objects are… • Mass • Distance

  26. Law of Universal Gravitation • The force of gravity acts between all objects in the universe.

  27. Strength of Gravity…

  28. Chapter 2, Section 3 • Newton’s Third Law states that for every action there is an equal and opposite reaction. • Momentum is defined as an object’s mass times its velocity (Momentum = mass x velocity). • The units for momentum is kgxm/s

  29. Law of Conservation of Momentum • The total momentum of two or more objects that interact don’t change. • It is the same before and after an event. (train cars) • The total momentum of any group of objects remains the same unless outside forces act on the objects (friction)

  30. Law of Conservation of Momentum

  31. How is momentum conserved? • http://youtu.be/y2Gb4NIv0Xg

  32. Chapter 2 Section 5 • Centripetal force causes an object to move in a circle

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