# Projectile Motion

## 18 terms

### Projectile Motion

Free Fall & Motion in Two Directions

### Free fall

is the condition in which an object is acted on by gravity (its weight) alone.

### A projectile

is any object that moves through air or space acted on only by gravity (and air resistance, if any)
free fall=projectile

### motion of a projectile

may be linear or curved (more specifically, parabolic in shape)

### trajectory

The path of a projectile

### linear projectiles

Objects that are falling
Objects thrown directly upward that rise and fall back down.

### acceleration for projectiles

all projectiles experience exactly the same amount
9.8 m/s2 down

POSITIVE
+9.8 m/s2

### upward sign

its velocity should be negative

### parabolic motion

2 components:
Horizantal=Constant
Vertical=under acceleration

### horizontal component

NOT under the influence of the acceleration of gravity
remains constant

### vertical component

IS under the influence of the acceleration of gravity
changes over time.

### horizontally launched projectiles

constant horizontal velocity
vertical Vi=0
will increase by 9.8 m/s2

### hang time

the total time projectile spends in flight

### upwardly launched

change direction mid-flight
slowing down on the way up, stop momentarily, speed up on the way down

### velocities of u-l

+velocity going down
because we want 9.8 to be positive and g is a down force
-velocity going up

### launch speed

scalar
initial launch speed=final landing speed because speed has no direction
vi= --launch speed
vf= ++launch speed

### projectile height

d=1/2at² only works when the vi is 0
consider the second half of the journey--at rest until landing using half hang time