Physics L3 www.slideshare.net/DMS_physics

Free Fall … occurs if the only force on an object is gravity. Acceleration of gravity For convenience we can use g = 10 m/s 2

… occurs if the only force on an object is gravity.

Acceleration of gravity

How Fast ? 10t t . . . . 50 5 40 4 30 3 20 2 10 1 0 0 Instantaneous Speed (m/s) Elapsed Time (s)

How Fast ?

Question What would the speed of the apple be after 4.5s? after 8s? after 15s? 10t t . . . . 50 5 40 4 30 3 20 2 10 1 0 0 Instantaneous Speed (m/s ) Elapsed Time (s)

What would the speed of the apple be

after 4.5s?

after 8s?

after 15s?

Speed Graph In Uniform Motion speed is directly proportional to time The graph is a straight line The slope is acceleration

In Uniform Motion

speed is directly proportional to time

The graph is a straight line

The slope is acceleration

Question What would the speed of the apple be after 4.5s? after 8s? after 15s? 45 m/s 80 m/s 150 m/s

What would the speed of the apple be

after 4.5s?

after 8s?

after 15s?

45 m/s

80 m/s

150 m/s

Acceleration is 10m/s 2 downwards at all times At the same height Speeds are the same Velocities are in the opposite directions t = 3s, v = 0m/s t = 2s t = 1s t = 0s t = 4s t = 5s t= 6s t = 7s v = 20m/s v = 10m/s v = 30m/s v = 40m/s

Acceleration is 10m/s 2 downwards at all times

At the same height

Speeds are the same

Velocities are in the opposite directions

t = 3s, v = 0m/s t = 2s t = 1s t = 0s t = 4s t = 5s t= 6s t = 7s v = 20m/s v = 10m/s v = 30m/s v = 40m/s

t = 3s, v = 0m/s t = 2s t = 1s t = 0s t = 4s t = 5s t= 6s t = 7s v = 20m/s v = 10m/s v = 30m/s v = 40m/s

Average Speed For objects moving with constant acceleration , the average speed is the arithmetic mean (average) of the initial and final speeds. 10t t . . . . 50 5 40 4 30 3 20 2 10 1 0 0 Instantaneous Speed (m/s ) Elapsed Time (s)

For objects moving with constant acceleration , the average speed is the arithmetic mean (average) of the initial and final speeds.

How far ?

How far ? 5t 2 t . . . . 125 5 80 4 45 3 20 2 5 1 0 0 Distance (m) Elapsed Time (s)

Classwork (p.20/Q) An apple falls from a tree and hits the ground in one second. What is its speed upon striking the ground? What is its average speed during this 1s? How high above the ground was the apple when it was dropped?

An apple falls from a tree and hits the ground in one second.

What is its speed upon striking the ground?

What is its average speed during this 1s?

How high above the ground was the apple when it was dropped?

Homework Assignment P.26 / 16,17,19 For a freely falling object dropped from rest, what is the Instantaneous speed at the end of the fifth second of fall? Acceleration at the end of the fifth second of fall? Distance covered by the end of the fifth second of fall?

P.26 / 16,17,19

For a freely falling object dropped from rest, what is the

Instantaneous speed at the end of the fifth second of fall?

Acceleration at the end of the fifth second of fall?

Distance covered by the end of the fifth second of fall?

End L3 www.slideshare.net/DMS_physics