1. BELLWORK 10/3/2016
If you drop a feather and a hammer on the moon, will they fall at the same rate?
Why or why not?

2. Hammer and Feather

3. Free-Fall Acceleration
A free falling object is an object that is falling under the sole influence of gravity. There are two important motion characteristics that are true of free-falling objects:
1. Free-falling objects do not encounter air resistance.
2. All free-falling objects (on Earth) accelerate downwards at a rate of 9.81 m/s2 (often approximated as 10 m/s2.

4. 6.7 Falling and Air Resistance
Air resistance does not depend upon the weight of the object.
6.7 Falling and Air Resistance
The amount of air resistance force an object experiences depends on the object’s speed and exposed surface area.
1. Speed
The greater the speed, the greater the air resistance.
2. Exposed Surface Area
The greater the surface area, the greater the air resistance.

5. Free- Falling Bodies g= -9.81 m/s2
If there is NO AIR RESISTANCE, ALL objects, regardless of weight & size, will fall at the same acceleration.
The Acceleration due to gravity: (Free-fall acceleration)
g= m/s2

6. Position Of Free Falling Object At Regular Time Intervals
The position of the free-falling object at regular time intervals, every 1 second, is shown. The fact that the distance which the ball travels every interval of time is increasing is a sure sign that the ball is speeding up as it falls downward.

7. Velocity Of Free Falling Object At Regular Time Intervals
Assuming that the position of a free-falling ball dropped from a position of rest is shown every 1 second, the velocity of the ball will be shown to increase.

8. ACCELERATION vs. VELOCITY
What will the acceleration of the ball be at
t = 1s? t = 4s?
At what time will velocity be the greatest?

9. FINAL VELOCITY vf = vi + gt
The velocity of a free-falling object which has been dropped from a position of rest is dependent upon the length of time for which it has fallen. The formula for determining the velocity of a falling object after a time of t seconds is:
vf = vi + gt

10. Solving for Final Velocity
A boy drops a ball from the roof of a house which takes 3.0 seconds to hit the ground. Calculate the velocity before the ball crashes to the ground.

11. Final Velocity Vf = Vi + gt Vf = 0 + -9.8 m/s ( 3s)
Vf = -2.9 x 101 m/s or 2.9 x 101 downward
The longer an object falls - the greater its velocity

12. Distance
The distance which a free-falling object has fallen from a position of rest is also dependent upon the time of fall. The distance fallen after a time of t seconds is given by the formula below:
Δy = (1/2) a ( Δt)2

13. Solving for distance
A boy drops a ball from the roof of a house which takes 3.0 seconds to hit the ground. Calculate the distance the ball has traveled.

14. Answer Δy = ½ gt2 = .5 (-9.8 m/s2) (3.0s )2 = -4.9 x 9s
= -4.4 x 101 m or 4.4 x 101 m, downward

15. This Week’s Schedule Monday and Tuesday– Work on Lab
Wednesday– Egg Drop
Thursday – Chapter 2 Test
Friday – Lab Journal Due
Egg Drop Rubric
Egg Drop On Time with Safe landing -100
Egg drop On Time with Cracked Egg – 94
Egg drop Late with Safe Landing – 80
Egg drop Late with Cracked Egg – 74
USE YOUR CLASS TIME WISELY!!!!!!!!!