#### Forces and Motion

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Transcript Forces and Motion

Forces and Motion
Force
• A force is a push or pull on an object.
(measured in Newtons)
• Sets an object in motion, changes its speed, or
changes its direction.
– Gravity
– Friction
Motion
• Motion is the change in the position of an
object.
• To observe motion, a reference point is used.
– A stationary object which can be used to measure
motion.
http://www.youtube.com/watch?v=ExjbcUmmc
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Speed
• Speed is the distance an object moves in a
certain time period.
• Velocity is the speed of an object IN A GIVEN
DIRECTION.
• To solve for speed, take the distance and
divide the time.
Solving for Speed
• If Mr. Cleland runs 10 meters in 2 seconds,
what is his speed?
– 5 m/s
• If Mr. Parke throws a baseball 12 meters in 4
seconds, what is the speed of the ball?
– 3 m/s
• Time=distance/speed.
• Distance=time x speed.
• If Mr. Whiting runs 15 meters at a speed of 3
m/s, what how long did it take him?
– 5 seconds.
• If Ms. Hetrick runs for 5 seconds at a speed of
4 m/s, how far does she go?
– 20 meters.
Graphing Motion
• You can show the motion of an object on a
line graph where you plot distance vs time.
• X axis is the time.
• Y axis is the distance.
• The slope of two points on a line will tell you
the speed.
• Different slopes tell the different speeds of an
object.
Acceleration
• The rate at which velocity changes.
– If speed changes, direction changes, or both.
• Acceleration is final speed – starting speed
then dividing by time.
• If Mrs. Greiser is driving her Mercedes and
accelerates from 10 m/s to 16 m/s in 3
seconds, what is her acceleration?
– 2 m/s^2
• If Mr. Stevenson is driving his Ford on the
freeway at 66m/s and hits a pothole, slowing
the vehicle to 44m/s in 11 seconds, what is his
deceleration or negative acceleration?
–
-2m/s^2
• If a plane increases speed from 300 m/s to
450 m/s in 5 s, what is its acceleration?
• A rocket is launched and reaches the speed of
7,000 m/s in 15s. What is its acceleration?
• Mr. C drives 200 km at a speed of 20 km/hr.
How long did it take him?
• Mr. C drives 200 km at a speed of 20 km/hr.
How long did it take him?
• Mrs. Swafford accelerates from 200 m/s to
350 m/s in 5 seconds. What is her rate of
acceleration?