• Will you be calculating an instantaneous speed or an average speed of a car that passed through the lines? Justify.

• Using the formula,

If you see a police officer at the white lines, what variable in the formula (not speed) are you able to manipulate to change the speed through the lines? Explain.

• Could there have been error on your part in taking the data? Explain.

POST LAB QUESTIONS:

time

distspeed

•DISTANCE

•SPEED

•AVERAGE SPEED

•INSTANTANEOUS SPEED

•CONSTANT SPEED?time

distspeed

DEFINE:

A pair of identical balls are simultaneously released on a pair of equal length tracks, A and B, as shown. Friction is minimal. Which ball will reach end of track first?

QUESTION

Compare the motion of the tapes for the:i)top situation ii)bottom situation.

VELOCITY vs SPEED

• Velocity =

•Sign of velocity (+ or - )•Negative doesn’t•Minus (-)

Ways to accelerate:

ACCELERATION

• Occurs when

Describe the motion of each spark tape.

ACCELERATION or DecelerationAn object that has a ZERO acceleration means

the velocity of the object is _________________.

What two kinds of possible motion could occur with a zero acceleration?

Constant Acceleration means an object is changing its velocity by _______________

Acceleration tells velocity how

Deceleration means

Constant Acceleration Equations

2

2

1atd

atv Assume all objects start from rest.

adv 22

Example An airplane accelerates down a runway at 3.2 m/s2 for 32.8sec until it finally lifts off the ground.a)Determine the distance traveled before takeoff.b)Determine the takeoff speed.

A sheep accelerates uniformly across the HS courtyard from rest to a speed of 7.1m/s over a distance of 35.4m.

Example

a) Determine the acceleration of the sheep.

b) Calculate the time it took to accelerate.

Heavy vs Light objects

Which falls faster?

GALILEO VS ARISTOTLE

FREEFALL andACCELERATION DUE TO GRAVITY

Earth’s gravitational pull causes objects to change velocity (accelerate or decelerate).

The change in velocity due to Earth’s gravity is called Acceleration Due To Gravity.

Freefall is a condition where an object is ONLY experiencing Earth’s gravitational pull with NO air resistance or minimal air resistance. The object can be moving downwards or upwards.

The Acceleration Due To Gravity is CONSTANT.

Value of Acceleration Due To Gravity is 10.0 m/s2

Gravity acts downward. Slows you down on way up. Speeds you up on way down.

rounded

Acc due to gravity = ‘g’Freefall equations

2

2

1gtd

gtv gdv 22

2/10 smg

*These equations are only good if object falls from rest

Gravity causes objects to EITHER gain speed downward or lose speed moving upward (a=g=10m/s2 ). What is speed of the ball at the peak of flight?

What is the acceleration of the ball on the way up?

What is the acceleration of the ball on the way down?

What is the acceleration of the ball at the peak?

Determine his speed after 35sec of freefall.

How far did he fall in that time?

a) Calculate his speed after falling 40ft. Convert ft to meters.

b) Calculate the time of fall for 40ft. Convert ft to meters.

a) Dwight Howard’s had vertical leap of 39.5”. Determine how much time it would take to fall that distance from rest. b) Calculate how fast he takes off based on the time from above.

A person holds a red ball while standing in an elevator. If the cable snaps and elevator begins to fall, what happens to the ball if person releases it while falling?

NO such thing as zero ‘g’

i. Why is there no zero ‘g’?

ii. Why is the term used if it is a false statement?

iii. What is it about freefall that makes people think gravity has reduced to a zero value?