On the Curves

Section 4.6

Investigate: Part A Toy Car with String What kept it moving in a circle? What happened when you let go of

the string? Which way did the string pull?

Investigate: Part A

Car on Road What keeps it moving in a circle? Which way would it move if nothing

keeps it moving in a circle?

Investigate: Part A

Car on Road Vectors

Investigate: Part B

What happened as you spun the stopper faster?

What happened as you made the string shorter?

What happened when you added more mass?

Investigate: Part C

Fc = mv2/R

Fc: Centripetal Forcem: Massv: VelocityR: Radius

Investigate: Part C

The gentler the curve, the _____ the force required to keep the car moving along the curve.

If the curve is tight (R is very small) then a _____ is required

Physics TalkCentripetal Force and Newton’s First Law

Centripetal Force and Newton’s Second Law

Physics TalkHow to find acceleration of an object moving in a circlea = v2/R

Physics TalkWhat keeps an object moving in a circle?

VocabularyCentripetal Force – a force directed towards the center that causes an object to follow a circular path.

VocabularyCentripetal Force: PracticeA roller coaster car is traveling east at 20 m/s. After 16 s, it is traveling north at 20 m/s. The circular curve had a radius of 200 m. Calculate the acceleration of the car.

Physics TalkCentripetal Force When you held the string of the toy

car? When a roller coaster car is upright? When a roller coaster car is tilted? When a car is on the road?

Physics TalkCentripetal Force IT IS NOT AN ADDITIONAL FORCE!!!

Physics TalkCentripetal Force ROLLER COASTER

Required Centripetal

Force

Force of gravity

(weight)

Normal force (force

of track)At the top of the loop 5000 N 1000 N

At the bottom of the loop

9000 N 10,000 N

Physics TalkThree Locations used for summarizing forced and weightConstant speed:

Physics TalkThree Locations used for summarizing forced and weightNet force at bottom of loop:

Physics TalkThree Locations used for summarizing forced and weightNet force at top of loop:

Physics TalkClothoid loop - a loop with a big radius at the bottom and a small radius at the top

Physics TalkClothoid loop: WHY?!

Physics TalkSAFETY!!!What is the cutoff for “g’s”?WHY?!