1. Do Now:
1. Mr. Rao went deep water solo diving in Thailand. He falls straight down from a height of 9.5 meters. What is his time of fall?

2. Aim: How do objects behave that travel in a circle?
HW: Circular Motion WS

3. Misconception
The doors to the “Gravitron” close and it starts to spin.
You are pushed against the outside edge of the ride and
pinned there, You must be experiencing “centrifugal
force” throwing you outward from the ride! Right?

4. Can you explain what is really happening?
As the Gravitron starts to spin,
friction between your body and the ride
start you moving vc Fc
Once you are moving, your body wants
to go STRAIGHT
… but you can’t…
The WALLS push you back in toward
the center of the ride!

5. Does a car accelerate around a turn?
Lets say you have a car traveling at a speed of 100 km/h. Is it accelerating?
Yes, but but how?
No change in speed, but change in velocity!
As car goes around a curve, the direction of velocity changes and acceleration is actually inwards. Show this through drawing.
a = ΔV/Δt

6. Velocity Vector What kind of force is acting on our car?
Without a force there would be no change in direction!
Change in velocity goes from each arrow top to the next and on original vectors points inwards from base of first 3 arrows. Force must be acting in the same direction as our change in velocity, which also is the direction of acceleration.
Whole point of vectors is to show that this change in velocity is actually towards the center and so is everything else!

7. Centripetal Force Demo
Centripetal Force- Center seeking force, directed towards center.
Centripetal Acceleration- Center seeking accel.
Velocity- Tangent the path travelled!
From kinematics… what is average velocity?
V = d/t… right? How about for a circular motion?
Demo with stopper and ball on string.

8. How can we describe circular speed?
Objects traveling in circular motion have SPEED
How do we define SPEED?
What is “Δd” and Δt???

9. Question!
What is the velocity of a tetherball hit around a pole with a radius of 1 meter and a period of 0.27 seconds? 2πr = 6.28 m T = 0.27 second VC = 23.3 m/s

10. How can we calculate Centripetal Acceleration?
Centripetal force provides an unbalanced, net force
toward the center of a circular path
Unbalanced forces cause ACCELERATION
vc , Fc , and ac constantly
CHANGE DIRECTION, but not MAGNITUDE

11. Example #1 Determine the centripetal acceleration
of a toy ball swinging with a speed of
12 meters per second on the end of
a 1.44 meter long string.
ac = v2 / r
ac = (12 m)2 / (1.44 m)
ac = 100 m/s2

12. WHITE BOARD ACTIVITY! Determine the velocity of a car that
experiences a centripetal acceleration
of 6 meters per second2 as it moves through a
turn with a diameter of 10 meters.
ac = v2 / r
6 m/s2 = v2 / (5 m)
v = 5.48 m/s
What is the car’s period?
T = 5.73 seconds

13. Individual Group Quiz
How can a car have a constant speed around a turn, but still accelerate?
Draw a ball going in a circle. What is the direction of velocity, acceleration and force at a point on a circular path?
An ice skater skates around a circular bend or radius 3 meters with a velocity of 7 m/s. What is her centripetal acceleration?