We
will begin our study of physics with a study of
motion.

Look around you, and you will find that almost
everything is in motion: flying birds, running
people, falling books, etc. We will analyze their
motions and think about how fast the object moves and
how far.

Distance and displacement
are different. When you traveled 50 km to the East
and then 20 km to the West, the total distance you
traveled is 70 km, but your displacement is 30 km
East.

In physics, we say that distance is a scalar and displacement
is a vector.
Scalar has a magnitude and vector has both a
magnitude and a direction. Scalar is one dimensional
and vector is two dimensional.

QUESTION:
A car moved 50 km to the North. What is
its displacement?
(e.g. "10 km East")

QUESTION: A
car moved 20 km East and 70 km West. What is
the distance? km

Velocity shows how fast
an object is moving to which direction. Average velocity can be
calculated by dividing displacement over time.

For
example, when a car moved 50 km in 2 hours, the
average velocity is 25 km/h because .

The instantaneous
velocity shows the velocity of an object
at one point. For example, when you are driving a car
and its speedometer swings to 90 km/h, then the
instantaneous velocity of the car is 90 km/h.

QUESTION:
A car moved 20 km East and 60 km West in
2 hours. What is its average velocity? km/h

QUESTION: How
far will a car travel in 15 min at 20 m/s? km

A velocity-time
graph shows the relationship between
velocity and time. For example, if a car moves at
constant velocity of 5 m/s for 10 seconds, you can
draw a velocity-time graph that looks like this:

The area below the line represents the
displacement the object traveled since it can be
calculated by xy, or (time * velocity) which equals
to displacement.

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QUESTION:
Calculate the distance traveled by the
car. m

When
the car A is at 50 km/h and the car B is at 30 km/h
at opposite direction, the velocity of the car A
relative to the car B is 80 km/h.

QUESTION:
If you are walking at constant velocity
of 5 km/h and a car passed you by at the
speed of 20 km/h from behind, what is the
car's velocity from your viewpoint? km/h

QUESTION: If
you are running at constant velocity of 5
m/s, what is your relative velocity to Earth?
m/s