Uniform Circular Motion http://www.youtube.com/watch?v=TThIX7hk 5bo&feature=related

What do you know? What does UNIFORM CIRCULAR MOTION look like? Can you give a real world example? Are things in UNIFORM CIRCULAR MOTION accelerating? Is there a (non-zero) net force acting on an object engaged in UNIFORM CIRCULAR MOTION?

Uniform Circular Motion Constant speed Constant radius Continuous acceleration directed radially toward the center Speed = circumference/period S=2pr/T

Example 1 The blades of a blender are 3.0 cm long. The blender spins at a maximum rate of 80 revolutions per second. Determine the speed of the tips of the blades.

Example 2 A 30.0 kg child rides on the edge of a 10.0m diameter carrousel that makes 7.50 revolutions every 1.00 minutes. Compute the speed of the child.

Are object’s experiencing UCM accelerating?

What affects the magnitude of the acceleration?????

UCM Lab What is the mathematical relationship between centripetal acceleration (m/s/s) and speed(m/s) for an object undergoing UCM? Consider: If the independent variable is zero, should the dependent variable be zero?

ac vs speed and ac vs radius

UCM Lab What is the mathematical relationship between centripetal acceleration (m/s/s) and speed(m/s) for an object undergoing UCM? (Keep the radius constant) Consider: If the independent variable is zero, should the dependent variable be zero?

PLQ

Understanding the Lab When traveling in a circle, is an object accelerating? Which way? What happened to the centripetal acceleration when the speed doubled?

Like here…. https://www.youtube.com/watch?v=r5L5jiKo AJw

SFc vs Speed What is the mathematical relationship between centripetal Force (N) and speed(m/s) for an object undergoing UCM? (Keep the radius constant) Consider: If the independent variable is zero, should the dependent variable be zero?

Understanding the Lab What happens to the net centripetal force if speed doubles but the radius stays constant? What would happen to the net centripetal force if we keep speed constant, but double the radius? What would happen to the net centripetal force if we keep speed and radius constant, but double the mass of the object?

After Quick Lab In pairs, complete FreeBody Exercise #10 Copy the problem description and the completed diagram into your notes. Be sure to note any forces that balance

Graphs Showing relationships:

Equations for UCM S=2pr/T ac = S2/r SFc = m(S2/r)

Ex 1 The blades of a blender are 3.0 cm long. The blender spins at a maximum rate of 80 revolutions per second. Determine the speed and acceleration of the tips of the blades.

Ex 2 A 20.0 kg child rides on a horse that is 5.00m from the center of a carrousel that makes one revolution every 8.00 seconds. Compute the net force acting on the child. What is the direction of the net force? If the child was standing on the deck of the carrousel, instead of riding a horse, what type of force would provide the net force?

Can a Nissan Leaf perform like a Porsche?

What affects the max speed for a car around a curve?

UCM Problems, where SFc gets expanded ID what you must find Draw a FBD ID the inward force (Deal with the vertical forces if necessary) Use SFc = m(S2/r) Sub and solve

Ex1 How fast can a 1200kg car travel around a 100m radius arc if the coefficient of _______ friction is 0.8? What if the car’s mass doubled, but all other factors remained the same?

Ex2 The Taz Twister is a ride at Great Adventure that consists of a round room with carpeted walls. Once the room is up to speed the floor is lowered, but the riders, who feel “pinned to the wall” do not drop with the floor. If the radius of the room is 7.0m, and the coefficient of ______ friction between the riders and the wall is 0.5: what speed must the riders have to stay “glued to the wall”? what Period must the ride have?