Transcript Speed and Velocity

Speed and Velocity
Drag racing videohttp://www.youtube.com/watch?v=ryDYYGI1cwg
Speed
• speed describes how quickly something
moves.
• 4 different types of speed
1. instantaneous speed – how fast you are
going at a certain point or time.
• example: radar gun or speedometer
JSD- fastest
speed
through a
photo gate
2. average speed –
looks at the average
speed between two
points or times.
• example: driving
from Olympia to
Seattle
• what we will
calculate in this
class
3. constant speed – speed stays the same
• example: cruise control
• the slope of a line is the ratio of the
“rise” to the “run”.
4. Terminal speed (velocity) – the speed at which
an object will stop accelerating when dropped
• example: a sky-diver
•
Peregrine Falcon video
http://www.youtube.com/watch?v=j3
mTPEuFcWk&NR=1&feature=fvwp
Velocity
• They Might be Giants clip
http://www.youtube.com/watch?v=DRb5PSxJerM
• velocity is speed with direction (N, S, E, W,
up, down, left, right)
• positive when moving forward (to the right
from an outside observer), and negative
when moving backward (to the left to an
outside observer).
JSD– walk at
constant
speed and
then change
direction
Math for Velocity or Speed
v = d/t
or
v=d÷t
v = velocity
d = distance
t = time
• Unit of measurement is a distance unit over a time unit
• cm/s, m/s, miles/hour, ft/year, miles/hour
• if a velocity, should include direction (N, S, E, W)
5-Step Method to Solving Word Problems
in Physical Science
1. Identify what you know (given)
2. Write down the correct formula to use
3. Show your work (“plug and chug” using
calculator)
4. Write down answer
5. Make sure answer has a unit of
measurement
Example problems
• A bike travels 70 meters West in 6.5 seconds.
Calculate its velocity.
Given
d=70m
t=6.5sec
formula
v=d/t
show work
70m/6.5sec
answer w/ units
10.8 m/sec West
• A car travels a distance of 100 miles in 2.2 hours.
Calculate its speed.
Given
d=100 miles
t=2.2 hours
formula
show work
answer w/ units
v=d/t 100miles/2.2hours 45.5 miles/hour