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Chapter 2 Motion and Speed

Motion Section 1. Motion and Position-Motion occurs when an object changes its positionDistance-how far a object has moved; important part of describing the motion of an objectSI Unit of Length= Meters (m), Kilometers (km). Displacement. Displacement-is the distance and direction of an objects c

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Chapter 2 Motion and Speed

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    1. Chapter 2 Motion and Speed Mr. Robinson, Instructor

    2. Motion Section 1 Motion and Position-Motion occurs when an object changes its position Distance-how far a object has moved; important part of describing the motion of an object SI Unit of Length= Meters (m), Kilometers (km)

    3. Displacement Displacement-is the distance and direction of an objects change in position from the starting point.

    5. Speed Speed is the distance an object travels per unit of time Rate-Any change over time is called a rate

    6. Calculating Speed

    8. Motion with Constant Speed If a car neither slows down nor speeds up, the car is traveling at a constant speed

    9. Changing Speed Much of the time, the speeds you experience are not constant.

    10. Average Speed Average speed is the total distance traveled divided by the total time of travel. It can be calculated using the relationship among speed, distance, and time. For a bicycle trip just described, the total distance traveled was 5km and the total time was ¼ h, or 0.25h The average speed was:

    11. Speed = distance/time S=d/t

    12. Instantaneous Speed Instantaneous speed is the speed at a given point in time

    13. Graphing Motion A distance-time graph makes it possible to display the motion of an object over a period of time

    14. Plotting a Distance-Time Graph Plotting a distance-time graph is simple The distance is plotted on the vertical axis and the time on the horizontal axis Each axis must have a scale that covers the range of numbers you are working with

    15. Velocity Velocity includes the speed of an object and the direction of its motion

    16. Motion of Earth’s Crust Moves very slow You can not detect its motion Can see evidence of its motion over long period of time The Theory of Plate Tectonics-the positions of landmasses have changed during millions of years

    18. Moving Continents Plates move so slowly that their speed are given in units of centimeters per year The San Andreas Fault moves at about 1cm per year Australian Plate’s movement is not of the fastest, pushing North about 17cm per year

    19. Acceleration Section 2 Just as speed is the rate of change of position, acceleration is the rate of change of velocity When the velocity of an object changes, the object is accelerating Velocity includes the speed and direction of an object

    21. Acceleration Acceleration can be either speeding up or slowing down Speeding up = Positive Acceleration (+) Slowing Down = Negative Acceleration (-)

    22. Calculating Acceleration The SI unit for velocity is meters/second (m/s), and the SI unit for time is seconds (s) Unit for acceleration is ”meters per second/second or m/s2

    24. Amusement Park Acceleration Roller coasters are constructed of wood and steel Wooden coaster do not have high velocities and acceleration as do steel coasters Wood is not rigid as steel Wooden coasters have to have steep hills or inversions loops to propel at high speeds

    25. Wooden roller coasters have swaying motion, steels don’t Steel coasters offer multiple steep drops and inversion loops, greater acceleration Accurate toward the grown @ 9.8 m/s2 A faster roller coaster goes from 0 to 160.9 km/h in 7 s

    27. Motion and Forces Section 3 What is a Force A force is a push or pull that one body exerts on another The applied force results in the movement of the ball

    28. Changing Motion A force can cause the motion of an object to change

    29. Balanced Forces In balanced forces the forces are equal and in opposite directions Forces on an object that are equal in size and opposite in direction are called balanced forces No motion

    31. Unbalanced Forces When forces of unequal strengths are pushing in opposite directions The result is a net force Unbalanced force=unequal in size and/or are not in the same direction

    32. Adding Forces When forces are pushing in the same direction, the forces add together

    33. Inertia and Mass Inertia is the tendency of an object to resist any change in its motion If an object is moving, it will keep moving at the same speed and in the same direction unless an unbalanced force acts on it

    34. Newton’s 1st Law of Motion Forces change the motion of an object in specific ways Newton’s laws of motion “a moving object at a constant velocity keeps moving at that velocity unless a net force acts on it” This law is called “the law of inertia”

    35. What happens in a crash The law of inertia can explain what happens in a car crash Car travels @ 50 km/h, collides head-on to a solid, it stops in 0.1s Car stops…YOU don’t …passenger stops 0.02 s later 50 km/h = falling from a three-story building

    36. Seat Belts The force needed to slow a person from 50 km/h to zero in 0.1 is equal to 14 times the force that gravity exerts on the person

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