Transcript Free Fallllllllllllllllllll

Free Fallllllllllllllllllll
What is Free Fall?
Are these both examples of free fall?
Free Fall
Do you need a parachute to skydive?
You don’t need a parachute to skydive.
You need a parachute to skydive twice.
Crazy
What is Free Fall? (cont.)
 Free Fall = The ideal falling motion of a body in
which gravitational force is the only force acting on
it.
 Gravity is accelerating the object.
 Acceleration due to gravity = -9.8 m/s2
Gravity & Direction
 Acceleration due to gravity is negative because it acts
toward the center of Earth.
 Up will be the + direction and down the – direction.
 Therefore
g= -9.8 m/s2
0s
1s
0m/s
Velocity vs. Time
-9.8m/s
2s
-19.6 m/s
3s
-29.4m/s
4s
-39.2m/s
What happens to the velocity
(vf ) of object after equal and
consecutive units of time (Δt)?
Answer…
The object gains speed at the
same rate (-9.8m/s2) in each
successive equal time
interval.
1
Displacement vs. Time
3
5
What happens to the displacement
(Δd) of an object in equal and
consecutive units of time (Δt)?
Answer…
7
More distance is covered in
each successive equal time
interval.
What Goes
Must Come
WGUMCD Properties
 Acceleration due to gravity
 Motion will occur in two directions
 Acceleration MUST represent its direction
(- 9.8 m/s2)
 Initial velocity will be given (velocity the object is
launched upward)
 Velocity up / Acceleration down = object will be
slowing down
WGUMCD Properties (cont.)
 Object will gradually slow down as it travels upward
 At its highest point…the object stops moving for a
split second


Vf = 0.0 m/s
D = displacement from point of launch to where the object
stops moving
WGUMCD Key Point
Symmetry
WGUMCD Symmetry
 Time:
 The time traveled up = the time traveled down
 Velocity:
 The velocity at each specific time interval up = the
velocity at each specific time interval down (must keep
in mind direction…when traveling down, velocity is (-).
Solving WGUMCD Problems
 Use the same formulas used for kinematic, free fall problems
 Time to max height: Vf = Vi + at (Vf will be 0 at top of flight)
 Velocity at a specific time: Vf = Vi + at
 Max height reached: Δd = Vit + ½ at2
(Vf will be 0 at top of flight)
 Total time in motion: Symmetry (time up = time down)
 Vf at impact: Symmetry (remember sign is direction of the
velocity)