1. How do we solve a free fall problem with kinematics?
Do Now:
HW:

2. Kinematics Charts
Alex Rodriguez is running from an angry mob of Redsox fans. His initial speed is 6 m/s, but he then breaks his hip (again) and decelerates at a rate of -2 (m/s)/s until reaching a final velocity of 0 m/s. How long did he run before getting caught?
Always make a chart!
Vf = Vi + at Vf Vi a t

3. G.U.E.S.S Method
G-Given Variables U-Unknown Variables E-Equations S-Substitute S-Solve

4. Other Important Motion Equations
Make sure they know acceleration is constant for third equation!

5. How can we define gravity?
Gravity is a force which can be defined as - a push or pull on an object toward the center of Earth..
Acceleration due to gravity is -9.8 (m/s)/s on EARTH!
Moon is -1.6m/s/s and jupiter is -26m/s/s

6. Mr. Galileo Why did both objects fall at the same rate?
Dropping Hammer and Feather on Moon
Why did both
objects fall at the
same rate?
2. If we dropped a
flat piece of paper
and penny which
would land first here?

7. Uses for “g”
An object falls from rest. Calculate its velocity at the end of one second. Two seconds. Three seconds.
t = 0
vi = 0 m/s
t = 1 s
v = m/s
v = m/s
t = 2 s
t = 3 s
v = m/s

8. DEMO: Picket Fence Drop

9. Top 5 Facts for objects thrown straight up & free fall!
“g” is ALWAYS -9.8 m/s2
If thrown up, the velocity is zero at max height!
Time going up = Time going down
All kinematic equations may be used for vertical projectiles… EXCEPT V = d/t and
V = (Vf + Vii)/2
Even at max height when final velocity is zero, “g” is still -9.8 m/s2

10. Falling Objects
A stone is thrown vertically upward with a speed of 18.0 m/s. How fast is it moving when it reaches the height of 11 m? How long is required to reach this height? *Acceleration Down is – Why are there two answers for how long it takes? Vf Vi d t a
Always make a kinematics chart!!!
Use Vf^2 equation for first part…
Figure out distance it takes to reach the peak by plugging in for Vf = 0, then take time of fall to 11 m with other equation.

11. Summary What are all the motion equations we deal with?
What is important about the equations in this course?
What are key facts in any vertical projectile question?
2. Know how to use them and why!