Transcript Linear Motion

Principles of Physics

motion along a straight line path, motion in
one dimension
 Which way are you headed?
 How far did you go?
 How fast are you going?
 Is your speed changing?
Velocity
 Rate at which position changes
 In other words, how quickly the position of an
object changes during the time interval
 Measured in meters per second (miles per
hour in the USA)
v

d
t
Velocity is calculated
d
v
t
v = average velocity (m/s)
d = displacement (m)
t = time (s)
 Average because we don’t know exactly what is happening
from the 1st position to the next
▪ The object could be speeding up and slowing down along the way

Vector quantity – has direction
 Direction is + when right, up, north, or east
 Direction is – when left, down, south, or west


Instantaneous speed = speed at any particular
point
Can be determined by speedometer, but not
d
by v 
t
1.
Rick walked 50 m in 60 s. What was his average speed?
Givens:
d = 50 m
t = 60 s
v=?
v
v
d
t
d 50m

t
60s
0.833m / s
2. A car has an average velocity of 20 m/s east. How long would it take the car to
travel 85 m?
Givens:
v = 20 m/s
t=?
d = 85 m
v
d
t
 d   85m 
t  

 v   20m / s 
4.25s
3. Anna watches a thunderstorm from her window. She sees the flash of a
lightning bolt and begins counting the seconds until she hears the clap of
thunder 10.0 seconds later. Assuming that the speed of sound in air is 330
m/s, how far away was the lightning bolt? (Assume that she sees the bolt
instantaneously).
Givens:
v = 330 m/s
t = 10 s
d=?
v
d
t
d  vt  330m / s(10s)
3300 m