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?