Module 9

  1. reference piont
    a point against which position is measured
  2. vector quantity
    a physical measurment that contains directional information
  3. scalar quantity
    a physical measerment that does not contain directional information
  4. acceleration
    the time rate of change of an objects velocity
  5. free fall
    the motion of an object when it is falling soley under the influence of gravity
  6. If an object's position does not change relative to a reference point is it in motion relative to that reference point?
    no  ** In order for motion to occur, an object's position must change. Since the object's position is not changing, it is not moving relative to the reference point.
  7. A glass of water sits on a counter. is it in motion?
  8. A child is floating in an inner tube in a still lake. His position does not change relative to a tree on the shore. He watches two girls jog along the shore of the lake. The girls keep perfect pace with each other. Neither is pulling ahead of nor falling behind the other.

    A. relative to whom is the child in motion?
    B. relative to whom is the first girl in motion?
    C. relative to whom is the second girl not in motion?
    • A. the girls
    • B. the child
    • C. the first girl
  9. What is the speed of a boat that travels 10 miles in 30 minutes? Answer in miles per second. * speed = distance/ time*
    20 miles per hour
  10. What is the speed of a jogger who jogs 6 kilometers in 45 minutes? answer in meter per munite.
    2.22 mps
  11. Lable each as a vector scale or a scalar  quantity.
    a. 10 meters 
    b. 1.2 meters /second2
    c. 3.4 feet/hour and slowing
    d. 56 liters
    e. 2.2 miles/ minute west
    f. 2.2 mm/year
    • a. scalar
    • b. vector
    • c.scalar
    • d. scalar
    • e. vector
    • f. scalar
  12. A car and a truck are traveling north on a highway. The truck has a speed of 45 miles per hour and the car 57 miles per hour. If the truck is ahead of the car what is the relative velocity? * relatyive velocity = relative speed - or + relative speed.*
    • 12 miles away from each other.  
    • equation: 57 - 45 = 12 mph
    • * Since the car is traveling faster than the truck, it is catching up to the truck.  Thus, the relative velocity is 12 mph towards each other.
  13. If an object travels for 15 minutes with a constant velocity of 12 miles per hour west what is the acceleration? * acceleration =  final velocity - intintial velocity / time*
    zero acceleration
  14. A sports car goes from a velocity of zero to a velocity of 12 meters per second east in just 2 seconds. What's the acceleration?
    6 meters per second2 east
  15. A train takes a long time to stop. that's what makes trains so dangerous to people who cross the tracks when one is near. If a train is traveling at 30 miles per hour south and takes 12 minutes to come to a stop, what's the train's acceleration?
    -150 miles per hour2
  16. A very picky physicist states that it is impossible for any object to experience free fall near the earth's surface . Why is he technically correct?
    Air resistance is a second influence, and all objects experience air resistance.
  17. Even though the physicst in the other question is right, why do we go ahead and assume heavy objects are in free fall when they fall near the earth's surface?
    The effect of air resistance is so small on heavy objects that is usually can be ignored.
  18. A long vertical glass tube contains a feather and a penny. All the air is pumped out and the tube is inverted causing them to fall. which one hits the ground first?
    they hit the ground at the same time
  19. What is the height of a building ( in meters) if it takes a dropped rock 4.1 seconds to fal from its roof?
    82.4 meters
  20. A hot air balloon drops a rock from his balloon. It takes 7 seconds for the rock to fall to the ground. What is the balloons altitude in feet?
    784 feet
  21. A scientist decides to study acceleration of an object moving in a straight line. He measured the distance the object travels in 30 second time intervals. The scientist notices that in each interval the object travels a shorter distance than it did before. Is the direction of the acceleration the same as or oppostite of the velocity?
Card Set
Module 9