Transcript Accelerated Motion

Acceleration
is the rate of
change
In velocity
Velocity and Acceleration
vi
+
+
+ or 0
a
+
+
0
- Or +
0
0
Motion
Speeding up
Speeding up
Slowing down
Slowing down
Constant
Speeding up
from rest
Remaining at
rest
Average acceleration is the
Change in velocity during some
Measurable time interval.
vf – vi
Δv
a=
=
tf – ti
Δt
The SI unit for acceleration is
m/s2
A sprinter begins a race at 0.0 m/s
And finished at 4.0 m/s. He does
This in a time of 8s.
What is his acceleration?
0.5 m/s2
Instantaneous acceleration is
The change in velocity at
An instant of time.
A velocity-time graph is a graph
That show velocity on the
y-axis and time on the x-axis.
The slope of a V-T graph will
Give you acceleration.
There are a bunch of new formulas
That can be found by deriving
Them from the two basic formulas
That we already know.
Displacement with
Constant Acceleration
ΔX = ½ (vi +vf)Δt
A racing car reaches a speed of
42 m/s. It then begins a uniform
Negative acceleration, using its
Parachute and brakes, and comes
To a stop 5.5s later. Find how far
The car moves while stopping.
120 m
Velocity with
Constant Acceleration
vf = vi + aΔt
Displacement with
Constant Acceleration
Δx = viΔt + ½a(Δt)2
A plane starting at rest at one end
Of a runway undergoes a constant
Acceleration of 4.8 m/s2 for 15s
Before takeoff. What is its speed at
Takeoff? How long must the
Runway be for the plane to
Take off?
72 m/s
540 m
Final Velocity after
Any displacement
vf2 = vi2 + 2aΔx
A babysitter pushing a stroller
Starts from rest and accelerates
At 0.500 m/s2. What is the
Velocity of the stroller after it
Has traveled 4.75 m?
2.18 m/s
Equations for constantly
Accelerated straight line motion
Form to use when
accelerating object has
initial velocity.
Form to use when
accelerating object starts
from rest.
Δx = ½ (vi +vf)Δt
Δx = ½(vf)Δt
vf = vi + aΔt
vf = a(Δt)
Δx = viΔt + ½a(Δt)2
Δx = ½a(Δt)2
vf2 = vi2 + 2aΔx
vf2 = 2aΔx
Free fall is the
motion of an
Object falling
with a Constant
Acceleration due
To gravity.
All free falling bodies
undergo
A uniform acceleration
Of 9.81 m/s2.
This acceleration, a, is given
The new symbol, g.
A construction worker accidentally
Drops a brick from a high scaffold.
What is the velocity of the brick
After 4 seconds? How far does the
Brick fall during this time?
39 m/s
78 m