Forces in Motion Review by malj


									Forces in Motion Review

        Chapter 2
How fast?                            Newton    Can you
            Definitions   Pick me!
9.8 m/s/s                             who?    read this?

  100         100          100       100        100

  200         200          200       200        200

  300         300          300       300        300

  400         400          400       400        400

  500         500          500       500        500
How fast? 9.8 m/s/s for 100?

• If the acceleration due to
  gravity were somehow doubled
  to 19.6 m/s/s, what would
  happen to your weight?

 Your Weight would Double!!
How fast? 9.8 m/s/s for 200?

• A 12 kg rock falls from rest off a
  cliff and hits the ground in 1.5 s.
  • a. Ignoring air resistance, what is
    the rock’s velocity just before it
    hits the ground?
                      14.7 ms/s

  • b. What is the rock’s weight after it
    hits the ground? (Hint: Weight is a
    measure of the gravitational force
    on an object.)
                   It stays the same
How fast? 9.8 m/s/s for 300?

• A rock climber dislodges a
  stone while climbing a
  mountain. The stone falls
  straight down, taking exactly
  3.5 s to hit the ground. Ignoring
  air resistance, how fast was the
  stone traveling when it hit the
                 9.8 x 3.5= 34.3m/s/s
How fast? 9.8 m/s/s for 400?

• Which of the following is an example
  of free fall?
• a. a skydiver falling from an airplane
• b. a falling or “floating” astronaut in
  orbit around Earth
• c. a ball falling from a rooftop
• d. tossing a set of keys to a friend

How fast? 9.8 m/s/s for 500?

• A ball is dropped from a rooftop.
  What is the ball's velocity after
  3 s? (Assume that there is no air
• a. 0 m/s    c. 19.6 m/s
• b. 9.8 m/s d. 29.4 m/s

Definitions for 100?

• Define Terminal Velocity in your
  own words
Definitions for 200?

• Define Free Fall in your own
Definitions for 300?

• Define inertia in your own
  words. Which Law is inertia
  directly related to?
Definitions for 400?

• Define Newton’s 3rd law of
  motion. Name three
  activities/sports that show this
Definitions for 500?

• Mass x Velocity is also known
  as what???
Pick me for 100?

• Explain why results differ on the
  moon and on Earth when a
  hammer and a feather are
  dropped from the same height
  at exactly the same time.

    There is no air resistance on the moon
    acting on the feather
    They would fall at same rate
Pick me for 200?

• Newton's third law of motion states that if
  a force is exerted on an object, another
  force occurs that
• a. is equal in size and opposite in
• b. is in the same direction and size.
• c. is equal in speed and opposite in
• d. is in the same direction and speed.

Pick me for 300?

• A golf ball and a bowling ball are moving at
  the same velocity. Which has more
• a. the golf ball, because it has less mass
• b. the bowling ball, because it has more
• c. They both have the same momentum
  because they have the same velocity.
• d. There is no way to know without
  additional information.

Pick me for 400?

• According to Newton’s first law of
  motion, a moving object that is not
  acted on by an unbalanced force will
• a. remain in motion.
• b. transfer its energy to another
• c. eventually come to a stop.
• d. accelerate in the absence of
Pick me for 500?
• Astronauts “fall” or appear to
  float inside the space shuttle
  because they
• a. are massless.
• b. have no gravitational force
  acting on them.
• c. are in free fall.
• d. are weightless.
Newton who for 100?

• How is inertia related to
  Newton's first law of motion?

  which is what
 the 1st law suggests
Newton who for 200?

• How does Newton's third law
  explain how a rocket takes off?

        Equal and opposite forces
        Rocket’s thrust DOWN
        Rocket goes UP
Newton who for 300?

• Explain why friction can make
  observing Newton’s first law of
  motion difficult.

Friction is always the unbalanced
force hear on earth
Newton who for 400?

• Use Newton’s third law to
  explain how a person using a
  hammer to drive a nail into a
  board is demonstrating
  conservation of momentum.
 Action – Swinging Hammer
 Reaction- Nail moves into wood
 Momentum is transferred into nail
 Newton who for 500?

 • How does Newton's second law
   explain why it is easier to push
   a bicycle than to push a car
   with the same acceleration?

The car has much more mass than the bike
so it would require much more force
Can you read this for 100?

•   Air resistance is
•   a. sliding friction.
•   b. rolling friction.
•   c. fluid friction.
•   d. static friction.
Can you read this for 200?

• Which of the following games
  uses conservation of
• a. billiards
• b. bowling
• c. baseball
• d. all of the above
Can you read this for 300?

• Is it just as hard to catch a thrown bowling ball as
  it is to throw it?
• a. The bowling ball has more inertia while in
  motion so it's harder to catch it.
• b. The bowling ball has the same inertia whether
  it's standing still or moving, so throwing it and
  catching it are both equally difficult.
• c. The bowling ball has less inertia while in
  motion, so it's easier to catch than it is to throw.
• d. Inertia has nothing to do with how easy or hard
  it is to throw or catch a bowling ball. It just
  depends on how strong you are.
Can you read this for 400?

• The picture below shows a common desk
  toy. If you pull one ball up and release it, it
  hits the balls at the bottom and comes to
  a stop. In the same instant, the ball on the
  other side swings up and repeats the
  cycle. How does conservation of
  momentum explain how this toy works?

                   The total momentum is transferred
                   Into each ball as it moves and stays the
                   Same throughout until friction stops it
Can you read this for 500?

                  Daily Double!!
•   You are a passenger in a car that is moving
    rapidly down a straight road. As the driver
    makes a sharp left turn, you are pressed
    against the right side of the car. Explain why
    this happens.

•   The design of a car can make a big
    difference in its maximum speed. Explain
    why two cars that have the same mass and
    are powered by the same type of engine
    might be able to reach very different speeds
    on the same road.
           Final Question
                                Distance fallen during this
Time (s)     Velocity m/s
   0               0                         0

   1       v = 1 × 9.8 = 9.8                4.9

   2       v = 2 × 9.8 = 19.6         4.9 + 9.8 = 14.7

   3               ?               4.9 + 9.8 + 9.8 = 24.5

   4               ?                 4.9 + 3(9.8) = 34.3

   5               ?                         ?

   6               ?                         ?

   7               ?                         ?
           Final Question
                                Distance fallen during this
Time (s)     Velocity m/s
   0               0                         0

   1       v = 1 × 9.8 = 9.8                4.9

   2       v = 2 × 9.8 = 19.6         4.9 + 9.8 = 14.7

   3        3 x 9.8 = 29.4         4.9 + 9.8 + 9.8 = 24.5

   4         4 x 9.8= 39.2           4.9 + 3(9.8) = 34.3

   5         5 x 9.8 = 49            4.9 + 4(9.8) = 44.1

   6        6 x 9.8 = 58.8           4.9 + 5(9.8) = 53.9

   7        7 x 9.8 = 68.6           4.9 + 6(9.8) = 63.7

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