Transcript Forces in Motion Review

Forces in Motion Review
Chapter 2
How fast?
9.8 m/s/s
Definitions
Pick me!
Newton
who?
Can you
read this?
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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
ground?
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
B
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
resistance.)
• a. 0 m/s
c. 19.6 m/s
• b. 9.8 m/s d. 29.4 m/s
D
Definitions for 100?
• Define Terminal Velocity in your
own words
Definitions for 200?
• Define Free Fall in your own
words
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
law.
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
direction.
• b. is in the same direction and size.
• c. is equal in speed and opposite in
direction.
• d. is in the same direction and speed.
A
Pick me for 300?
• A golf ball and a bowling ball are moving at
the same velocity. Which has more
momentum?
• a. the golf ball, because it has less mass
• b. the bowling ball, because it has more
mass
• c. They both have the same momentum
because they have the same velocity.
• d. There is no way to know without
additional information.
B
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
object.
• c. eventually come to a stop.
• d. accelerate in the absence of
friction.
A
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.
C
Newton who for 100?
• How is inertia related to
Newton's first law of motion?
It means RESIST CHANGE
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?
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Air resistance is
a. sliding friction.
b. rolling friction.
c. fluid friction.
d. static friction.
C
Can you read this for 200?
• Which of the following games
uses conservation of
momentum?
• 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?
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•
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
second
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
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4.9 + 9.8 + 9.8 = 24.5
4
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4.9 + 3(9.8) = 34.3
5
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6
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7
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Final Question
Distance fallen during this
second
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