UNIFORM CIRCULAR MOTION UNIFORM CIRCULAR MOTION Uniform circular

UNIFORM CIRCULAR MOTION

UNIFORM CIRCULAR MOTION Uniform circular motion is motion along a circular path in which there is no change in speed, only a change in direction. v Fc Constant velocity V tangent to path. Constant force Fc toward center. Question: Is there an outward force on the ball?

UNIFORM CIRCULAR MOTION (CONT. ) The question of an outward force can be resolved by asking what happens when the string breaks! v Ball moves tangent to path, NOT outward as might be expected. When central force is removed, ball continues in straight line. Centripetal force is needed to change direction.

CIRCULATION MOTION The direction of the velocity vector at any instant is in the direction of a tangent line drawn to the circle at the object's location. (A tangent line is a line that touches a circle at one point but does not intersect it. )

CENTRIPETAL FORCE What is Centripetal Force? A force that acts on a body moving in a circular path and is directed toward the center around which the body is moving.

CENTRIPETAL FORCE Where is Centripetal Force pointed towards? Gravitational Force What is this Force called?

EXAMPLES OF CENTRIPETAL FORCE You are sitting on the seat next to the outside door. What is the direction of the resultant force on you as you turn? Is it away from center or toward center of the turn? Car going around a curve. Fc Force ON you is toward the center.

CENTRIPETAL FORCE Where is the Centripetal Force pointed towards? What is this force called? Force of Friction

PAP DERIVING ACCELERATION Definition: ac = Dv t = Centripetal acceleration: ac = v 2 R Dv t vf

EXAMPLE 1: A 3 -kg rock swings in a circle of radius 5 m. If its constant speed is 8 m/s, what is the centripetal acceleration? v v = 8 m/s R=5 m m ac = 12. 8 m/s 2 R What is the Force (F)? m = 3 kg ac = 12. 8 m/s 2 F = (3 kg)(12. 8 m/s 2) Fc = 38. 4 N

EXAMPLE 2: v = 15 m/s Fc R 450 N 30 m m=? Speed skater Solve for mass(m) F = mv 2/R FR = mv 2 FR/v 2 = m, Substitute m=(450 N)(30 m)/(15 m/s)2 m=60 kg

CIRCULAR MOTION-WALL OF DEATH

TO BE CONTINUED……………

WARM-UP QUESTIONS ANSWER THE QUESTIONS

For questions #1 -#5: An object is moving in a clockwise direction around a circle at constant speed. Use your understanding of the concepts of velocity, acceleration and force to answer the next five questions. Use the diagram shown at the right. Click the button to check your answers. 1. Which vector below represents the direction of the force vector when the object is located at point A on the circle? 2. Which vector below represents the direction of the force vector when the object is located at point C on the circle? 3. Which vector below represents the direction of the velocity vector when the object is located at point B on the circle? 4. Which vector below represents the direction of the velocity vector when the object is located at point C on the circle? 5. Which vector below represents the direction of the acceleration vector when the object is located at point B on the circle?

NASCAR VIDEO http: //science 360. gov/obj/tkn-video/5 f 385 cf 55046 -4279 -984 e-27 f 911 c 6 ca 07

NASCAR VIDEO QUESTIONS 1. Explain in a minimum of 6 sentences, the different forces a race car experiences while it is going in speeds in excess of 200 mph. around a turn. Include a picture with these different forces.

TO BE CONTINUED……. .

REVIEW- CIRCULAR MOTION

UNIFORM CIRCULAR MOTION REVIEW The question of an outward force can be resolved by asking what happens when the string breaks! v Ball moves tangent to path, NOT outward as might be expected. When central force is removed, ball continues in straight line. Centripetal force is needed to change direction.

REVIEW Constant velocity (V) tangent to path. Constant force Fc toward center. Acceleration (a) is in the same direction as Fc, towards the center

REVIEW Centripetal acceleration: Centripetal Force: ac = v 2 R