1. 4*7 Circular motion: riding on the curves
WDYS??? /
WDYT???
You DO NOT fall out of the roller-coaster when it goes upside down during a loop because _____.

2. 4*7 Investigate (p420) Part A: Moving on Curves
1a) The car runs in a _____.
1b) With string attached to car, it now runs in a __.
1d) When string is cut from car, it now runs in a __.

3. 4*7 Investigate (p420)
A FORCE is needed for CIRCULAR MOTION… WITHOUT the force, the object moves in a STRAIGHT LINE
2a) The _____ in the string supplies the force.
2b) The force is _____ the center of the circle.

4. There must be a force pointing toward the center of the curve…
4*7 Investigate (p420)
There must be a force pointing toward the center of the curve…
3. The force of _____ between the _____ and the _____ keeps the car moving in a circle.
4. Draw the diagram:

5. 4*7 Investigate (p420)
The force moving the cart in a circle will be _____ the center of the circle.
5c) Draw the free- body diagram:

6. 4*7 Investigate (p422) Part B: How much force is required?
1a) The force is acting _____ the center of the circle.
1b) With ONE stopper…
As you begin to twirl the stopper, your fingers __________ to supply a force!!!

7. ***This is an example of a _____ relationship***
4*7 Investigate (p422)
2a) NOW with THREE stoppers…
As you INCREASED the mass, your fingers __________ to supply a _____ force
***This is an example of a _____ relationship***
As the mass increases, the force _____.
2b) You can only measure ONE VARIABLE (mass) at a time!!!

8. 4*7 Investigate (p422) 3a) A SMALL circle with ONE stopper…
As you begin to twirl the stopper, your fingers __________ to supply a force!!!
NOW, a LARGER circle with ONE stopper…
As you INCREASED the length/radii, your fingers __________ to supply a _____ force

9. ***This is an example of a _____ relationship***
4*7 Investigate (p422)
***This is an example of a _____ relationship***
As the length/radii increases, the force _____.
3b) You can only measure ONE VARIABLE (length/radii) at a time!!!

10. 4*7 Investigate (p422)
Why don’t you fall out of the roller coaster cart when it goes upside down during a vertical loop???
5a) As the speed increases, a _____ force is needed to keep it moving in a circle.
5b) As the mass increases, a _____ force is needed to keep it moving in a circle.
5c) As the length/radii decreases, a _____ force is needed to keep it moving in a circle.

11. On to Vertical Loops… 4*7 Investigate (p422)
4b) Force of fingers when stopper is near the TOP of the circle = __________
Force of fingers when stopper is near the BOTTOM of the circle = __________
4c) What happens (to the shape) when the string and stopper lose speed???

12. 4*7 Notes(p425): Centripetal Force and Acceleration
All objects moving in circles/curves:
Require a force toward center of circle
Are accelerating
EXAMPLE string supplies the force
track pushing on wheels
Normal Force (FN)  force toward center of circle/curve, its perpendicular in direction

13. ***Centripetal Force is NOT an additional force***
Centripetal Force  force that keeps object moving in a circle/curve; its always directed toward center
EXAMPLE force (tension)= string attached to car force (friction)= b/t tires and road
force (gravity)= Earth orbits around Sun
***Centripetal Force is NOT an additional force***

14. Fc = (m × v2 ) r Centripetal Force and Acceleration
(Part B Investigate)
Centripetal Force is LARGER if:
Speed is increased (Direct)
Mass is increased (Direct)
Radius of circle is decreased (Indirect)
Fc = (m × v2 ) r
Fc = centripetal force (N) m = mass of object (kg)
r = radius of circle (m) v = speed of object (m/s)

15. EXAMPLE contact force b/t you and seat
Newton’s 2nd Law  if there is a net force, then an object must be accelerating (speed up/slow down/change direction)
Centripetal Acceleration  acceleration directed toward the center of circle/curve
EXAMPLE contact force b/t you and seat
***It’s the centripetal acceleration and
contact force that give you the THRILL***

16. 2. Apparent Weight and the Roller-Coaster Ride “Apparently LIGHTER” 
Top of loop
Contact force is smaller
Acceleration is directed downward
“Apparently HEAVIER” 
Bottom of loop
Contact force is greater
Acceleration is directed upward

17. 3. Safety on the Roller Coaster
1 g = 10m/s/s  normal gravity
2 g = 20m/s/s
4 g = 40m/s/s  this is the maximum acceleration for a roller coaster!!!
6 g = 60m/s/s  this is what astronauts experience at lift-off!!!
9 g = 90m/s/s causes unconsciousness!!!

18. In a vertical loop, the DIRECTION OF CENTRIPETAL FORCE (FC) is always changing to ensure that it is always TOWARD THE CENTER OF THE CIRCLE

19. Draw a Vertical Loop:
FC =centripetal force FN = normal force FW = weight/gravitational force

20. 4*7 TOTD If the speed and mass INCREASES, then the force __________.
If the size of the circle INCREASES, then the force __________.
The THREE factors that make it possible to go UPSIDE-DOWN are:
3. __________
4. __________
5. __________

21. 4*7 Checking up (p429):
_____ is required to make an object travel in a circle.
You (are/are not) accelerating if you are traveling in a circle at a constant speed.
At the top of a roller coaster loop, the two forces that provide the centripetal force are 1._____ and 2._____
The force responsible for your apparent weight on a roller coaster is _____.
The centripetal force acting on an object depends _____ on the object’s mass. It varies _____ with the radius of the curve. It _____ with the square of the object’s velocity.

22. 4*7 Physics to Go (p433): A) B)
An object moving in a circle at a _____speed requires a ______ centripetal force.
It (will/will not) be more difficult to make the turn because the mass has increased. A larger mass requires a _____ centripetal force.
8. Draw and Label the picture…AGAIN!!!

23. 4*7 Physics to Go (p433): 10. 14.a) b) c) d) e) f) g) Fast-moving
Roller
Coaster 
Required Centripetal Force
Force of Gravity (Weight)
Normal Force
Top of Loop
4000N
500N
Bottom of Loop
6000N
Slow-moving
Roller
Coaster 
Required Centripetal Force
Force of Gravity (Weight)
Normal Force
Top of Loop
800N
Bottom of Loop
2800N