Transcript Projectile Motion - Dr. Haleys Physics Class

projectile - Any object moving
through air and affected only by
gravity
ex: a kicked soccer ball in the air, a stunt
car driven off a cliff, and a skier going off a
ski jump.
trajectory - the path a projectile
follows
The trajectory of a projectile is a special
type of arch- or bowl-shaped curve called
a parabola.
The range of a projectile is the
horizontal distance it travels in
the air before touching the
ground.
If you were asked to
calculate the range of a
projectile, what would you
be calculating?
Projectile motion is
two-dimensional because both
horizontal and vertical motion
happen at the same time.
The horizontal and vertical
components of a projectile’s
velocity are independent of
each other.
Does the horizontal
component affect the
vertical component?
Does the vertical
component affect the
horizontal component?
Both speed and direction change as a
projectile moves through the air.
The motion is easier to understand by
thinking about the vertical and horizontal
components of motion separately.
The complicated curved motion problem
becomes two separate, straight-line
problems like the ones you have already
solved.
x component – velocity problems
v = d/t
y component – acceleration due to
gravity problems
d = Vi(t)+1/2 a t2
Is a ball rolling off a
table a projectile?
Yes,
yes it is.
Let’s look at the horizontal and
vertical components of this
projectile
Once the ball becomes a
projectile it feels no horizontal
force, so its horizontal velocity
is constant.
What does that mean?
It moves the same distance
horizontally each second, it’s
speed does not change
It moves horizontally in the air
just as it would on the ground.
A projectile’s horizontal velocity does
not change because no horizontal
force acts on it.
The vertical motion of the ball is
accelerating because of gravity. The
ball is in free fall in the vertical
direction.
What is the ball’s rate of
acceleration?
Just like other examples of free fall,
the ball’s vertical speed increases
by 9.8 m/sec each second.
A projectile’s
vertical velocity
increases by
9.8 m/sec each
second.
What is happening to the
horizontal velocity of the ball?
What is happening to the
vertical velocity of the ball?
x component – velocity problems
v = d/t
y component – acceleration due to
gravity problems
d = Vi(t)+1/2 a t2
A stunt driver steers a car off a cliff at a
speed of 20 m/sec. He lands in the lake
below two seconds later. Find the
horizontal distance the car travels and the
height of the cliff.
An object is thrown off a cliff with a
horizontal speed of 10 m/sec. After 3 seconds
the object hits the ground. Find the height of
the cliff and the horizontal distance travelled
by the object.
A cat runs and jumps from one roof top to
another which is 5 meters away and 3 meters
below. Calculate the minimum horizontal
speed with which the cat must jump off the
first roof in order to make it to the other.