Bell Ringer 1.What does the slope of this graph show? 2.What is the acceleration from 4 seconds to 6 seconds?
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Bell Ringer
1. What does the slope of this graph show?2. What is the acceleration from 4 seconds
to 6 seconds?
P H Y S I C S
Objects in Free Fall and Gravity
Objectives:1)We will understand free fall, and how it is
impacted by gravity2)We will understand what forces act upon an
object that is thrown up into the air
Free Fall
Free Fall Motion of an
object when only gravity is acting on it.
Free-fall acceleration
The acceleration of an object due only to the effect of gravity
Acceleration Due to Gravity
g = -9.8 m/s2
(we’re going to use 10 m/s2)
Objects go 10 m/s faster each second
Negative Velocity downward movement
v = 0 m/s
v = -9.8 m/s
v = -19.6 m/s
v = -29.4 m/s
v = -39.2 m/s
t = 0 s
t = 1 s
t = 2 s
t = 3 s
t = 4 s
Human Breaks Sound BarrierWorld Free Fall Record 10/14/2012
Position and Velocity and Free Fall
t = 0 s
t = 1 s
t = 2 s
t = 3 s
t = 4 s
Position and velocity can be determined as a function of time
If you know the time and position, you can determine the velocity.
Skydivers
Which drops first?
Bowling Ball and Tennis Ball
Demo All objects accelerate at a constant rate of 10
m/s2 regardless of mass or weight
123 TIMES MORE!
Bowling Ball = 7 kg Tennis ball = 0.057 kg
1 Second Challenge
1 Second in Air “A” for the semester No tardies, cuts or absences
1.225 m in the air to get 1 s.
Jordan From Free-Throw Line
Jordan From Free-Throw Line
Time in Air = 0.98 s
Objects Thrown Upwards
Object thrown upwards experience the same:
g = -10 m/s2
10 m/s slower each second
Remember…
When you are speeding up… You have positive acceleration
When you are slowing down… You have negative acceleration
Vector A quantity, such as position, that has
both magnitude and direction
Acceleration Due to Gravityv = 0 m/s
v = +9.8 m/s
v = +19.6 m/s
v = +29.4 m/s
v = -9.8 m/s
v = -19.6 m/s
v = -29.4 m/s
v = -39.2 m/s
Velocity VectorAcceleration “g” Vector
Velocity Direction
Positive (+) value Up Negative (-) value Down
Peak of the Path
Maximum HeightVelocity = 0 m/s
Returning to Initial Height:Time up = Time downVelocity up = - Velocity down
Position vs TimeVelocity vs Time
• What is happening at the apex of the position vs time graph?
• What is happening in the velocity vs. time graph at the x-axis?
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