Transcript Vectors and Projectile Motion

Vectors and Projectile Motion
Vectors
Vectors are usually written as an arrow. It
represents a quantity with a direction.
Example: 50 mph East
or 10 mph West
Vectors can be combine by adding or subtracting
them. This is called the resultant vector, or net
vector.
Example: How fast was the plane going if it was
traveling 50 mph against a head wind of 10 mph?
50 mph East
10 mph West
Resultant or Net Vector
50 mph E
40 mph E
50 mph E
10 mph W
Subtract when
arrows are
opposite each
other.
25 mph E
75 mph E
Add when arrows
are in the same
direction.
What if the vectors are perpendicular to
each other?
We can use the
Pythagorean theorem:
a2 + b2 = c2
(20)2 + (60)2= c2
400 + 3600 = 4000 = 63.25 mph
20 mph S
a
Which direction?
South East
b
60 mph E
Just show the resultant vector with an
approximate magnitude and the proper direction.
Projectile Motion and Gravity
Projectile motion is a curved path that objects
take because they are pulled down by
gravity.
Gravity pulls all objects toward the earth. The faster
they are projected (shot out) the farther they will go
but will all curve toward the earth eventually.
If there was
no gravity the
cannon ball
would
continue in a
straight line.
Forward velocity
Gravitational
In what direction
pull
will the resultant
vector be?
This happens every moment
and the overall shape of the
line is a curve
Orbiting objects
An orbiting object has
enough forward velocity
so that by the time it
starts to curve and fall
toward the earth, the
earth is curving as well.
This means it never quite
gets to the ground. If the
forward velocity of an
orbiting object begins to
slow down. It will
eventually fall into the
earth.
Gravity
The strength of gravity depends on
two things:
1. The mass of the objects (m=mass)
2. The distance between them
(r=radius is like distance)
Centripetal Force
Centripetal force is a force that pulls you
toward the center of a curved or circular
path.
It is what causes cyclists to lean in as they go
around a curve.
Centripetal force takes different forms like:
• When a car curves around a corner the friction between
the car and pavement acts like centripetal force.
• The gravitational force that holds the planets in orbit is
centripetal force.
• The string that holds a ball as you swing it in a circle is
centripetal force.