Speed and Velocity Distance vs. Displacement You drive the path, and your odometer goes up by 8...
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Transcript of Speed and Velocity Distance vs. Displacement You drive the path, and your odometer goes up by 8...
Speedand
Velocity
Distance vs. Displacement
• You drive the path, and your odometer goes up by 8 miles (your distance).
• Your displacement is the shorter directed distance from start to stop (yellow arrow).
• What if you drove in a circle?start
stop
Speed
• Speed is distance / time
or more accurately
t
dv
t
dv
Time
• What is time?
Constant speed
• A moving object that doesn’t change it’s speed travels at constant speed
• Constant speed means equal distances are covered in an equal amount of time
Constant speed
Distance in cmPosition
• Shown as a series of dots (center of mass image)
1
4
3 4
5 6
7 8 9 10
11
12
Time in seconds
2 5 6
What is the speed?
Constant speed
• Shown as a graph
Time
Posi
tion
3 4 52
2
4
6
8
1
What is the speed of this object?
Calculating Speed
• Speed = Distance Time
• If a runner travels 100 m in 10 seconds what was his average speed?
• Probably not constant• Can solve for the other pieces too• Distance = speed x time• Time = Distance
Speed
Speed is a scalar quantity
• What is it missing?
• instantaneous velocity - the velocity that something has at any one instance
– (The terms instantaneous speed and avg. speed may also be used)
interval timentdisplaceme = velocity average
t
dv
_
The average velocity for a trip might be 53
miles/hour.
However, during this trip your instantaneous
speed might have been 0 miles/hour at a stoplight or 70
miles/hour on the open road.
Show All Work Including The EquationS and Units
SAWITESU
An object is goes 30m North in 13 seconds. What is its velocity?
SAWITESU
Key Concepts
t
dv Speed =
Velocity is a vector quantity: Speed and direction