Transcript Chapter 5 power point

Chapter 5
Matter in motion
I. Measuring Motion
A. Motion- Motion occurs when an object
changes position over time when compared to
a reference point.
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I. Measuring Motion
1.Common reference points include the earth,
buildings, trees, etc.
2. Moving objects can be reference points.
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www.biography.ms/ NASCAR.html
B. Speed- depends on the distance traveled
and the time taken to travel that distance.
1. The SI unit for speed is meters per
second (m/s). Other common speed
units are km/hr and miles/hr.
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2. Determining average speed. ( triangle
diagram) Speed = distance /time
How many different labels for speed can you think
of?
VIDEO-Science Investigations Physical Science:
Investigating Motion, Forces and Energy.
Discovery Channel School. 2004. unitedstreaming.
1 March 2006 <http://www.unitedstreaming.com/>
Speed practice problems
1. What is your average speed if you take 0.5
hours to walk 4000 m?
4000m/0.5h= 8000m/hr
2. The average speed of a car is 110km/h how
long will it take the car to travel 715 km?
715km/110km/h= 6.5hours
3. if you are traveling at 67km/h for 2.5
hours how far will you go?
67km/h x 2.5h= 167.5km
4. The train traveled 500 kilometers north to Odessa in 2 hours.
What is the train’s speed? What is it’s velocity?
Distance= 500 Km
Time = 2 hours
Speed = distance /time
Speed = 500km/2h
Speed = 250 km/h
Velocity = 250 km/h North
5. Jeremie ran around the track at the YMCA for 2 hours. When
he was done he figured that he had traveled 20 kilometers.
What was his speed? What was his velocity? Distance = 20 km
Time = 2 h
Speed = distance /time
Speed- 20km/2h
Speed =10km/h
Velocity = 0 ( he traveled in circles so there is no direction. No
direction no velocity)
Slope helps us to compare information on different
graphs.
The slope of a distance vs. time graph is
equal to the average speed.
Slope = rise / run
distance vs time
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distance
distance
distance vs time
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Rise is how far up the graph goes and run is how far over.
C. Velocity- Velocity is the speed of an object in a
particular direction.
1. Speed and velocity are not the same.
Velocity always includes reference
direction.
http://www.amadirectlink.com/news/2005/speed.asp
2. Constant velocity is always along a straight line.
Speed and direction do not change in constant
velocity.
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3. Velocities can be combined to determine resultant
velocity.
Martin’s notes on adding velocities.MP4
Speed velocity + acceleration video Basics of
physics united streaming .com 4 minutes
Ann is at the airport and is in a rush. She normally travels north
at 2 m/s. If she gets on a “moving sidewalk “ that travels at 2
m/s north and walks on it, what will be her resultant velocity?
2m/s North + 2 m/s North = 4 m/s North ( same direction
means addition)
Ann is traveling north. Is it better for Ann to take a place and
stand on a north moving sidewalk at 2 m/s or to walk north fast
at 3m/s on the empty south “moving sidewalk” that travels at
2m/s?
Standing on the north sidewalk is 0m/s you walking and 2m/s N
the sidewalk for a total of 2m/s north
Walking 3m/s North on the 2m/s south sidewalk is a subtraction
problem 3m/sN – 2m/s S= 1 m/s north It is north because that is
the bigger number
The north moving sidewalk is faster at 2 m/s total
D. Acceleration- Acceleration is the rate at
which velocity changes. The faster the
velocity changes, the greater the acceleration
is.
www.mouvup.com/.../ fr/demo/demoAcceleration.html
VIDEO-Science Investigations Physical Science: Investigating Motion,
Forces and Energy. Discovery Channel School. 2004. unitedstreaming. 1
March 2006 <http://www.unitedstreaming.com/>
1. Calculating acceleration:
Acceleration =
(Final velocity – Starting velocity)
(time it takes to change velocity)
-ORAcceleration = ∆ v / time to ∆ v
VIDEO-Science Investigations Physical Science:
Investigating Motion, Forces and Energy. Discovery
Channel School. 2004. unitedstreaming. 1 March 2006
<http://www.unitedstreaming.com/>
7. Acceleration would be shown on a
velocity vs. time graph.
velocity (m/s)
velocity vs time
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velocity
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time (s)
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2. The unit for velocity is m/s and time is s.
Acceleration is m/s/s.
3. Positive acceleration occurs when the
velocity increases.
4. Negative acceleration (deceleration)
occurs when the velocity decreases.
5. A change in direction, without a change
in speed, is acceleration also.
6. Circular motion is continuous acceleration.
a. Standing on the equator of the earth or
a windmill
b. Circular motion is known as centripetal
acceleration.
id.mind.net/.../ circularMotion.html
Extra practice on velocity and
acceleration problems
Jose travels 275 meters in 15 seconds. What
speed is he traveling at?
275/15 = 18.3m/s
2. How far will Jose have traveled in 5 seconds? In ten
seconds?
18.3 x5 = 91.5
3.Marta travels to Iowa city at 89 kilometers per hour.
It will take her 1 hour and 5 minutes to get to Iowa
City. How far away is it?
89X 1.08 = 96.12
1.
4. Mrs. Martin lives 20.93 Km from school. It takes her
25 minutes to get to school. If the speed limit is 55
km/hr is she speeding?
No , she is traveling at 49.8 km/h
25/60 to get hours = 0.42 distance/time 20.93/.42=49.8
5.Indiana Jones is on top of a truck traveling at 130
m/s. if he crawls along the top of the truck to the front
of it at 3 m/s what is his total velocity?
133m/s forward
6. If Indiana Jones falls under the truck and uses his
whip to control his speed under the truck as he moves
back to the back of the truck at 5m/s what is his total
velocity?
125m/s forward
7.Janice is walking her big dog at a rate of 2 m/s.
The dog sees a rabbit and drags Janice up to the
speed of 10 m/s in three seconds what was her
acceleration.
(10-2) / 3= 2.7m/s/s
8. Janice give the command to stop and her dog
does in 4 seconds. What was her acceleration.
(0-10) / 4 = - 2.5m/s/s
Why is it negative?
Because she is slowing down
II. What is Force?
A. Force- A force is a push or a pull.
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personal.stevens.edu/ ~mparagan/homepictures.htm
PUSH!
PULL!
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Video Push Pull -
Things in motion. Visual Learning Company (2004). Retrieved March 1,
2006, from unitedstreaming: http://www.unitedstreaming.com/
1. Forces have size and direction.
2. Forces are everywhere. If you see something
moving, a force caused the motion.
3. Newton- Forces are expressed using a unit
called the Newton (N).
4. The more Newtons, the greater the force.
Sir Isaac Newton (1642-1727).
Source: IRC
Copyright: 2005
B. Net Force- Net force is the force that results from
combining all the forces exerted on an object.
1. Forces in the same direction are added
together to find net force.
2. If opposing forces are in play, net force is
determined by subtracting the smaller
force from the larger one.
C. The net force on an object tells whether
the forces on the object are balanced or
unbalanced.
1. Unbalanced forces produce a change in motion.
(acceleration)
a. When the net force is not zero, the forces
are unbalanced.
b. Unbalanced forces are necessary to cause a
non-moving object to produce a change
in motion.
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2. Balanced forces produce no movement.
a. When the net force is equal to zero,
forces are balanced.
b. A house of cards has balanced forces
or….!
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III. Friction: A Force that
Opposes Motion
A. Friction- Friction is a force that opposed
motion between two surfaces that are
touching.
http://www.school-forchampions.com/science/friction.htm
VIDEO-United streaming .com friction 1:33
B. Friction occurs because the surface of objects is
rough.
1. Even objects that feel smooth have
microscopic “hills and valleys”.
http://ffden2.phys.uaf.edu/211_fall2002.web.dir/Ben_Towns
end/StaticandKineticFriction.htm
2. Friction between two surfaces depends on
the roughness and force pushing the
surfaces together.
3. Rougher surfaces create more friction,
smoother surfaces create less.
4. The greater the force pushing two objects
together, the greater the friction between the
two surfaces.
C. There are many types of friction.
1. Sliding friction. Sledding, Brakes
on a Bike, Writing with a pencil.
http://www.darvill.clara.net/enforcemot/friction.htm
2. Rolling friction. Anything with wheels.
http://www.school-for-champions.com/science/friction.htm
3. Fluid friction. Opposes the
motion of objects through
liquid or gas.
http://www.darvill.clara.net/enforcemot/friction.htm
4. Static friction. Force applied to
an object but does not move object.
D. Friction can be helpful or harmful.
1. List helpful and harmful friction
affecting a moving car.
2. Friction can be reduced between
objects.
a. Lubricants- reduce friction
between objects.
(motor oil, grease)
http://www.darvill.clara.net/enforcemot/friction.htm
b. Ball bearings- reduce friction
between wheels and axles.
http://science.howstuffworks.com/bearing3.htm
Inline skates &
skateboards
Conveyer belt
rollers
Stools and Lazy Susan
turntables
c. Sanding/smoothing objects to
lessen the “hills”.
woodstore.woodmall.com/ is16fe20.html
3. Friction can be increased between objects.
a. Rough up a surface- Sand on icy road.
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b. Increase the force between objects- Paper
weight, Scrubbing.
IV. Gravity: A Force of Attraction
(P. 125-129)
•
A. Gravity- Gravity is a force of attraction
between objects due to their masses.
(Demo TE125)
B. All matter is affected by gravity.
1. All matter has mass. Gravity is
a result of mass. Therefore all
matter experiences gravity.
2. Gravitational force pulls objects
toward each other.
3. The Earth’s gravity is so large it
affects everything on the Earth.
C. Law of Universal Gravitation states that all
objects in the universe attract each other through
gravitational force. The size of the force depends
on the masses of the objects and the distance
between them.
VIDEO-
Basics of Physics: Exploring Gravity. United Learning (2004). Retrieved March 1, 2006, from unitedstreaming:
http://www.unitedstreaming.com/
1. The moon has less mass than the Earth. You
would only weigh 1/6 as much on the moon!
2. Gravitational force decreases as distance increases.
D. Weight- Weight is a measure of gravitational
force exerted on an object.
1. Weight is expressed in the unit, newtons
(N).
2. Weight and mass are different. Weight is
the result of gravity pulling on a given
mass. Mass- Mass is the amount of
matter in an object.
United streaming weight vs. mass 57 sec