Transcript
Chapter 11: MotionChapter 11: MotionSection 1: Describing Motion
MotionMotion
Motion occurs when: ◦an object moves a
certain distance in a certain amount of time◦an object’s position
changes
DistanceDistanceDistance is how far something has movedMeasured in METERS, km, cm, mm, etc.
DisplacementDisplacement
Displacement is the change in position of an object
Also measured in METERS, km, cm, mm, etc.
SpeedSpeed
Speed is the distance an object travels over the amount of time it takes to travel
Measured in m/s (meters per second)Speed (m/s) = distance (m) ÷ time (s)
Calculating SpeedCalculating Speed1. After driving for exactly 60 seconds, you
have driven 600 meters. What speed were you driving?
2. After driving for 1 hour, you have driven 72 kilometers. What speed were you driving?
a. Calculate the speed in km/hrb. Calculate the speed in m/s
Constant & Changing SpeedConstant & Changing Speed
Constant speed means an object does not speed up or slow down.
Changing speed means an object gets faster or slower.
Average SpeedAverage Speed We usually calculate the average speed:
Average speed (m/s) = total distance (m) ÷ total time (s)
Yesterday, John Doe ran 6 km in 30 minutes. Sometimes he sped up and sometimes he slowed down. What was his average speed?
a. Convert 6km to m: 6km x 1000m/1km = 6000 mb. Convert 30 mins to sec: 30 min x 60sec/1min = 1800
secc. Calculate avg. speed: 6000 m ÷ 1800 sec = 3.33m/s
Instantaneous SpeedInstantaneous SpeedSpeed can be
measured at a certain point in time.
For instance, if you are driving, your speedometer may read 30 mi/hr.
You don’t have to drive for an hour for your car to know this – your speed is instantaneous.
Graphing SpeedGraphing Speed
Distance and Time are variables!◦Independent
Variable: time◦Dependent Variable:
distance
Graphing Constant SpeedGraphing Constant Speed
Graphing Changing SpeedGraphing Changing Speed
Graphing Changing SpeedGraphing Changing Speed
Graphing Changing SpeedGraphing Changing Speed
VelocityVelocityVelocity is a measure of an object’s
SPEED and DIRECTION.Velocity is measured by:
velocity = displacement ÷ time
v = d/t
Velocity & DisplacementVelocity & Displacement
If you run around a circular track and end up in the same position you started, your displacement is 0.
So is your velocity: v = 0/time, so v=0
Calculating VelocityCalculating Velocity
1. You walk down a winding road and end up 80 meters from your starting point. It took 1 minute and 20 seconds to walk from one end to the other. What was your velocity?
2. Was your speed greater or less than the velocity you calculated in #1?
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