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                                     3rd Quarter Benchmark Study Guide

Electricity and Magnetism

    1. An electric field is an area surrounding a charged object, within which the object can exert an
       electric force on another object without touching it.

    2. Induction is the build-up of a static charge in an object with the object is close to, but not
       touching, a charged object.

    3. Give an example of something getting charged by induction storm clouds charging the ground, a
       balloon near a charged wall, (anything that gets charged without touching)

    4. An electric charge will move between two positions with different potentials

    5. An electric current is a continuous flow of electric charge, which is measured in amperes.

    6. Explain how a person gets shocked a person gets a build-up of electrons which gives them negative
       chare, then they touch something usually a conductor causing static discharge

    7. Explain what has happened to a “dead” household battery all the chemical reactions have stopped

    8. Lightning travels the path of least resistance.

    9. Like particles repel while unlike particles attract

    10. How does an object with no net charge become charged? When it touches another neutral object
        that gives up electrons to it

    11. Static charge is the buildup of electric charge in an object caused by the uneven distribution of
        charged particles

    12. How are storage cells recharged? Chemical reactions that produce current are reversed

    13. A light bulb is the resistor in a circuit.

    14. A short circuit is an unintended and undesired path connecting one part of a circuit with another

    15. A continuous charge flows only when a circuit is closed

    16. A fuse is a protective device that breaks a circuit when too much current flows through it

    17. A series circuit is a circuit in which current follows a single path

    18. A parallel circuit is a cicuit in which current follows more that one path. Each device that is
        wired in a parallel circuit has its own path to and from the voltage source.

    19. How does a switch turn off a light? It breaks the circuit
Motion and Forces Ch 1

     20. Motion is a change in position over time

     21. How do you measure speed? Find the distance and divide it by time

     22. If you are riding a bicycle and you start pedaling faster, your speed will increase

     23. velocity is speed in a specific direction

     24. When an object is moving at a steady velocity the acceleration is equal to zero

     25. Acceleration is a measure of change in velocity

     26. Give an example of zero acceleration (anything going at a steady rate)

     27. What do you need to know in order to measure motion? A person’s position at different times

     28. Tom jogged 100 m in 5 seconds, then sprinted 200 meters in 5 seconds. What is Tom’s average

Average Speed = total distance / total time

S = (100 m + 200 m) / (5 s + 5 s)

S = 300 m / 10 s

S = 30 m/s

     29. Latitude and longitude measure position

     30. A reference point is a location to which you can compare other locations

     31. Speed is measured using the following units: km/hr, mi/hr, m/s

     32. You need to know direction and distance from a reference point to measure an object’s position.

     33. A girl runs 100 meters in 20 seconds. What is her speed? (show your work)
   5 m/s

     34. Velocity is speed in a specific direction

     35. Acceleration is the rate at which velocity changes with time.

Motion and Forces Ch 2

     36. If you increase force then acceleration increases

     37. Newton’s second law states that if you apply the same force but increase the mass of an object then the
         acceleration of the box will decrease
 38. Centripetal force is any force that is keeping an object moving in a circle.

 39. According to Newton’s third law when an object exerts a force on another object, the second object

exerts a force back on the first object that is equal in size and opposite in direction.

 40. A balanced force is equal forces on an object that do not cause the object to move.

 41. Action/reaction forces are force pairs that act on two different objects.

 42. Give an example of an action/reaction force. (answers will vary)
You jump up in the air. The action is your feet applying force to the ground
and the reaction is the ground pushing on your feet.

 43. Momentum is a measure of mass in motion.

 44. Collision is a situation in which two objects in close contact transfer energy and momentum

 45. What does it mean if momentum is conserved? The total momentum after a collision

is equal to the total momentum before the collision.

 46. Force can be described as a push or a pull

 47. A net force is all the forces acting on an object.

 48. You need to know mass and acceleration to calculate force.

 49. Inertia is the resistance of an object to a change in its motion.

  50. Give an example of zero net force being applied to an object
(answers will vary – anything that is a balanced force)

  51. Conservation of momentum is when the only forces acting on objects are
action/reaction pairs.

 52. An unbalanced force is forces that are applied unequally and cause an
object to have motion.

 53. You have to apply an unbalanced force to change the motion of an object.

  54. Write a sentence relating velocity and momentum The greater the velocity,
the greater the momentum.

 55. Gravity is a force

 56. If a book is laying motionless on a table, then the book has balanced forces acting on it.
57. What force is being applied to a 60 kg cart that is   58. What is the mass of a box that is being pushed at
accelerating at 4.2 m/s2? (show all of your work)         an acceleration of 5 m/s2 with a force of 70 N?

F = ma                                                    m = F/a

F = 60 kg x 4.2 m/s2                                      m = 70 N / 5 m/s2

F = 252 N                                                 m = 14 Kg

59. What is the velocity of a car that has a mass of      60. What is the velocity of a car that has a mass of
1400 kg and a momentum of 3080 kg m/s? v = P / m          1500 kg and a momentum of 3300 kg m/s? v = P / m

V=p/m                                                     V=p/m

V = 3080 Kg m/s / 1400 Kg                                 V = 3300 Kg m/s / 1500 Kg

V = 2.2 m/s                                               V = 2.2 m/s

   61. Newton’s first law is an object will only change its motion when an unbalanced force is applied to

     62. An example of Newton’s First Law is (answers will vary) Example – a soccer ball will remain
         motionless until someone applies an unbalanced (a kick) to it

     63. Newton’s Second Law is an objects acceleration depends on the object’s mass and the forces
         acting on it

     64. An example of Newton’s Second Law is (answers will vary) Example – If two carts have the same
         force applied to them but one is packed full and the other is empty, then the empty cart will
         accelerate faster

     65. Newton’s Third Law is for every action there is an equal and opposite reaction.

     66. An example of Newton’s Third Law is (answers will vary) Example – when a runner applies force
         to the ground the ground applies and equal force back on the runners foot.

Answer the following questions on a separate sheet of paper
    67. Two bumper cars collide. Use the collision of the cars to help you explain the conservation of
        momentum. Use the following terms in your answer: conservation of momentum, mass, velocity,
        outside forces.

   Before the collision, each bumper car has a mass and a velocity. These can be used to calculate the
   total momentum of the system. After the collision, the cars will have different velocities. If you
   calculate the new total momentum using these new velocities, the law of conservation of momentum
   states the new total momentum is equal to the original total momentum. If momentum is not
   conserved, there are outside forces acting on the system.
 68. A marathon runner wants to choose the best shoe for a race. She knows that she should consider the
     mass of the shoe as she makes her decision. Which of Newton’s laws should she consider and why?

According to Newton’s second law of motion, she should choose the shoe with the least mass. This is
because mass is closely related to inertia. The more massice an object, the more inertia it has, and the
more force it takes to get the object moving. It will take more force for the runner to move a more
massive shoe than a lighter one.

 69. Use Newton’s three laws of motion to explain why a child should not ride in the front seat of a car that
     has air bags.

In a collision, the child’s inertia would keep him going forward at the speed the car had been going,
according to Newton’s first law. When the air bag deploys, the child hits the air bag with a force
equal to his mass times his acceleration, according to Newton’s second law, while the air bag hits the
child with the force it exerts as it expands. The action-reaction force of this collision, according to
Newton’s third law, is great enough to cause harm to, or even kill, a small child.

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