Chapter 13 Lessons


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Chapter 13 Lessons

  1. 1. Chapter 13 Forces in Motion
  2. 2. You Will Discover: <ul><li>How motion is measured. </li></ul><ul><li>How force affect motion, work, power. </li></ul><ul><li>What Newton’s laws of motion are. </li></ul><ul><li>How simple machines make work easier. </li></ul>
  3. 3. Chapter 13 Vocabulary <ul><li>Velocity: the speed and direction of an object’s motion </li></ul><ul><li>Force: a push or pull that acts on an object </li></ul><ul><li>Work: energy used when a force moves on an object </li></ul><ul><li>Power: the rate at which work is done </li></ul><ul><li>Equilibrium : the state in which the net force is zero </li></ul><ul><li>Inertia: the tendency of an object to resist a change in motion </li></ul><ul><li>Acceleration: the rate at which the velocity of an object changes over time. </li></ul><ul><li>Machine: a device that changes the direction or the amount of effort needed to do work. </li></ul>
  4. 4. Lesson 1: How can you describe motion? <ul><li>Types of Motion </li></ul><ul><li>Steady or Constant - the Earth has steady motion as it moves around the Sun. </li></ul><ul><li>Variable - cars, trucks, and buses because they move in many directions and at many speeds. </li></ul><ul><li>Periodic - a pendulum, swings back and forth </li></ul><ul><li>Circular - wheels </li></ul><ul><li>Vibrational - a rubber band when you pluck it </li></ul>
  5. 5. Examples of Motion Steady or Constant Periodic Variable Vibrational Circular
  6. 6. Speed <ul><li>Average Speed: describes how far an object moves during a certain amount of time. </li></ul><ul><li>Average Speed = Distance </li></ul><ul><li> Time </li></ul><ul><li>The motion of an object cannot be measured by just looking at the object. </li></ul><ul><li>Motion is always measured in relationship with some location called a point of reference. </li></ul><ul><li>The speed at which a person is moving can vary according to which point of reference you use. </li></ul>
  7. 7. Speed Formula <ul><li>Point of Distance Time Speed </li></ul><ul><li>Reference </li></ul><ul><li>Train Car 10 m 5 s 10m = 2 m/s 5 s </li></ul><ul><li>Signal 150 m 5 s 150m = 30 m/s </li></ul><ul><li>Light 5 s </li></ul>
  8. 8. Velocity <ul><li>Speed and Velocity are not the same! </li></ul><ul><li>Velocity describes the speed and the direction of an object’s motion. </li></ul><ul><li>Example: the speed of the train might be described as 30 meters per second, but its velocity is 30 meters per second North. </li></ul>
  9. 9. Questions to Discuss <ul><li>What are five types of motion? Give an example for each one. </li></ul><ul><li>What do you need to know to find an objects velocity? </li></ul><ul><li>What is a point of reference? </li></ul><ul><li>If you were riding a bicycle, is your motion constant, variable, or periodic? Explain. </li></ul>
  10. 10. Lesson 2 - What are forces? <ul><li>Pushes and Pulls </li></ul><ul><li>A Force is a push or pull that acts on an object. </li></ul><ul><ul><li>When one object pushes or pulls another object, the first object is exerting a force on the second one. </li></ul></ul><ul><li>Forces can make a moving object speed up, slow down, or change direction. </li></ul><ul><li>Forces have both magnitude and direction. </li></ul><ul><ul><li>Magnitude is measured in newtons (N). </li></ul></ul><ul><ul><li>The direction of a force can be described by telling which way the force is acting. </li></ul></ul>
  11. 11. Gravity <ul><li>Every object in the universe exerts a gravitational pull on every other object. </li></ul><ul><li>An object’s weight is the amount of gravitational force between it and Earth. </li></ul><ul><li>-This depends on the object’s mass and Earth’s mass. </li></ul>
  12. 12. Magnetism <ul><li>Magnetism is a force that pushes or pulls on other objects . </li></ul><ul><li>Magnets will strongly pull on objects made of iron, cobalt, nickel, and gadolinium. </li></ul><ul><li>The north and south poles of </li></ul><ul><li>two magnets will push away </li></ul><ul><li>from each other. </li></ul>
  13. 13. Electricity <ul><li>Electric forces act between objects that are electrically charged. </li></ul><ul><ul><ul><li>Objects get electrically charged when they gain or lose electrons. </li></ul></ul></ul><ul><li>All atoms have negative electrons and positive protons. </li></ul><ul><ul><ul><li>If an object gains electrons , the object will be negatively charged. </li></ul></ul></ul><ul><ul><ul><li>If an object loses electrons, it will be positively charged. </li></ul></ul></ul>
  14. 14. Electricity <ul><li>Electrons move from one object to another when: </li></ul><ul><ul><ul><li>The objects are rubbed together. </li></ul></ul></ul><ul><li>Objects that are electrically charged will exert forces on each other. </li></ul><ul><li>Oppositely charged objects are attracted to each other. </li></ul><ul><li>Objects with the same charge are repelled from each other. </li></ul>
  15. 15. Friction <ul><li>Friction is the force that results when two materials rub against each other. </li></ul><ul><li>Friction acts to slow down the motion of an object or keep it from starting to move. </li></ul><ul><li>Friction depends on the qualities of the object involved. </li></ul><ul><ul><ul><li>The shape, speed, or texture of one object can affect the amount of friction. </li></ul></ul></ul>
  16. 16. Work <ul><li>Work is done when a force moves an object. </li></ul><ul><li>To calculate work: </li></ul><ul><li>Force x Distance = Work </li></ul><ul><li>Work is measured in joules. </li></ul>20 N x 2 m = 40 J 2 m 20 N 10 N x 2 m = 20 J 2 m 10 N 10 N x 1 m = 10 J 1 m 10 N Work Distance Force
  17. 17. Work <ul><li>If the force applied to an object, does not make the object move, then no work has been done. </li></ul><ul><li>Work is only done when the object moves. </li></ul><ul><li>Holding an object in place can require a force, but since the object doesn’t move no work is done. </li></ul>
  18. 18. Power <ul><li>Power is the rate at which work is done . </li></ul><ul><li>The faster work is done, the power is increased. </li></ul><ul><li>To calculate the amount of power: </li></ul><ul><li>Work = Power </li></ul><ul><li>Time </li></ul>
  19. 19. Questions to Discuss <ul><li>What are the causes of electrical and magnetic forces? </li></ul><ul><li>How does friction affect movement? </li></ul><ul><li>What are two examples of forces? </li></ul><ul><li>What kind of force can make a paper clip cling to a comb? </li></ul><ul><li>In what unit is work measured? In what unit is power measured? </li></ul>
  20. 20. Lesson 3 - What are Newton’s laws of motion? <ul><li>NET FORCES </li></ul><ul><li>Different forces can act on an object at the same time. </li></ul><ul><li>They may act in the same direction, different directions, and some may be stronger than others. </li></ul><ul><li>The combination of all these forces is the NET FORCE! </li></ul><ul><li>The net force determines whether the object start or stop moving or change direction. </li></ul>
  21. 21. Net Forces <ul><li>Equal forces working in opposite directions, balance those forces. The net force is zero . </li></ul><ul><li>This is called equilibrium. </li></ul><ul><ul><ul><li>A stationary object will remain motionless. </li></ul></ul></ul><ul><ul><ul><li>A moving object in will continue to move at a constant speed in a straight line. </li></ul></ul></ul><ul><li>Unbalanced forces acting on an object causes it to change motion. </li></ul>
  22. 22. Newton’s First Law <ul><li>Unless a net force acts on an object , the object will remain in constant motion. </li></ul><ul><li>An object at rest stays at rest until a net force acts upon it. </li></ul><ul><li>An object moving at a constant speed will continue to move in a straight line and at a constant speed. </li></ul>
  23. 23. Newton’s Second Law <ul><li>Acceleration is the rate at which the velocity of an object changes over time. </li></ul><ul><li>The net forces acting on an object can change an object’s velocity by causing it to speed up, slow down, or change directions. </li></ul><ul><li>The formula that describes the relationship between force, mass, and acceleration is: </li></ul><ul><li>Force = Mass x Acceleration </li></ul><ul><li>The stronger the force the more that object will accelerate. </li></ul>
  24. 24. Newton’s Third Law <ul><li>When one object exerts a force on a second object, the second object exerts a force on the first object. </li></ul><ul><li>This is sometimes called the action-reaction law of motion. </li></ul><ul><li>Action-reaction forces are always equal and opposite , and they occur in pairs . </li></ul>
  25. 25. Questions to Discuss <ul><li>What is the net force on an object? </li></ul><ul><li>What does an object look like that is in equilibrium? </li></ul><ul><li>What does Newton’s first law of motion state? The second law? The third law? </li></ul><ul><li>How does force affect acceleration? </li></ul><ul><li>Why do action-reaction forces always occur in pairs? </li></ul>
  26. 26. Lesson 4 - What are simple machines? <ul><li>Machines and Work: </li></ul><ul><ul><ul><li>Work is done when a force causes an object to move. </li></ul></ul></ul><ul><ul><ul><li>A machine is a device that changes the direction or the amount of force needed to do work . </li></ul></ul></ul><ul><ul><ul><li>Machines do not reduce the amount of work that needs to be done , it just makes it easier . </li></ul></ul></ul><ul><ul><ul><li>There are four types of simple machines: pulley, wheel and axle, lever, inclined plane </li></ul></ul></ul>
  27. 27. Pulley <ul><li>A pulley consists of a rope or cable that runs through a grooved wheel. </li></ul><ul><li>*Examples: </li></ul><ul><li>flag pole </li></ul><ul><li>drapery rods </li></ul>
  28. 28. Wheel and Axle <ul><li>A wheel and axle is made up of a circular object and a shaft. </li></ul><ul><li>*Examples: </li></ul><ul><li>steering wheel </li></ul><ul><li>door knob </li></ul>
  29. 29. Lever <ul><li>A lever is made up of a stiff bar that rotates around a fixed point called a fulcrum . </li></ul><ul><li> *Examples: </li></ul><ul><li>tongs </li></ul><ul><li>clothes pins </li></ul><ul><li>pliers </li></ul>
  30. 30. Inclined Planes <ul><li>An inclined plane consists of a flat surface with one end higher than the other. </li></ul><ul><li> *Examples: </li></ul><ul><li>screws, wedge, doorstop </li></ul><ul><li>ramps, </li></ul>
  31. 31. Complex Machines <ul><li>A complex machine uses two or more simple machines put together . </li></ul><ul><li>Many complex machines use electricity, gravity, burning fuel, human force, or magnetism to operate </li></ul><ul><ul><ul><li>Examples: </li></ul></ul></ul><ul><ul><ul><li> washing machine </li></ul></ul></ul><ul><ul><ul><li> go cart </li></ul></ul></ul><ul><ul><ul><li> car </li></ul></ul></ul><ul><ul><ul><li> s ailboat </li></ul></ul></ul>
  32. 32. Questions to Discuss <ul><li>Why is a screw considered a simple machine? </li></ul><ul><li>What is a complex machine? </li></ul><ul><li>How is the movement of rolling a weight up an inclined plane different from climbing stairs? </li></ul><ul><li>What is a machine? </li></ul><ul><li>List the four simple machines. What is one example of each simple machine? </li></ul>