M OTION. Motion is a change in position To determine a change in position you need a reference...
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M OTION. Motion is a change in position To determine a change in position you need a reference point, a point that is assumed to be stationary. The reference
Motion is a change in position To determine a change in
position you need a reference point, a point that is assumed to be
stationary. The reference point is used to create a frame of
reference, a coordinate system in which the position of objects are
measured.
Slide 3
D ISTANCE AND D ISPLACEMENT Distance is the total length
traveled by an object. It is always positive. Distance does not
have to be in a straight line. Displacement is the distance and
direction away from the starting point. It can be positive or
negative. Displacement must always be in a straight line. B=10 km C
= 20 km A=30 km
Slide 4
M OVEMENT We measure how far an object has moved, or its
distance, in meters
Slide 5
M OTION Motion includes three things: Distance Time Speed Speed
is the distance an object travels per unit of time. Speed =
distance/time or s=d/t The standard unit for speed is m/s or meters
per second
Slide 6
E XAMPLE A train traveling at a constant speed travels 800
meter in 100 seconds. How fast is the train moving?
Slide 7
E XAMPLE 1 speed= d/t d=800 m t=100s speed=800m/100s speed = 8
m/s
Slide 8
E XAMPLE 2 A man runs at a constant speed of 10 m/s. How long
does it take him to run 40 meters?
Slide 9
E XAMPLE 2 speed= d/t t=d/s d=40 m s=10m/s d=40 m/10 m/s t = 4
s
Slide 10
C ONSTANT VS. A VERAGE S PEED Speed is ususally not constant.
It can vary over the distance travelled. Average speed describes
the motion of an object when the speed is changing. Average speed
is equal to the total distance divided by the total time.
Instantaneous speed is the speed of an object at a certain point in
time.
Slide 11
V ELOCITY Velocity is the speed of an object and the direction
of its motion. v av = d / t = (d f - d i ) / (t f - t i ) - change
in value The difference between average speed and average velocity
is the addition of a direction. Bill was travelling at 60 miles per
hour. SPEED Bill was travelling north at 60 miles per hour
VELOCITY
Slide 12
M EASURING M OTION A speedometer gives the instantaneous speed
of a vehicle. The cruise control of a car helps to maintain a
constant speed.
Slide 13
G RAPHING M OTION A distance/time graph displays the motion of
an object over time meters seconds The height of a point on the
graph is how far it has travelled from the origin point. The slope
of a line is the speed. The steeper the line the faster the speed.
The average speed is the slope of the line connecting the starting
and ending points
Slide 14
V ELOCITY M INI -L AB Mark your starting point on the floor
with tape At the starting point one member will give the car a
gentle push. At the same time, another member will start the
stopwatch. Stop timing when the car comes to a complete stop.
Record the time. Mark the spot at the front of the car with a
pencil. Use a meterstick to measure the distance traveled. Write
down this number in meters. Calculate the speed of the car. Repeat
the process 4 times Next, once the car starts have the timer start
and call out every second for 5 seconds have the other group
memebers mark where the car is with their hand. Measure where the
car was and plot the informaion on a graph.