2 circular motion
- 1. Circular Motion motion of an object in a curved line (radius & speed are constant) 1. Objects traveling in a circle are accelerating. Why? Due to constantly changing direction!!! 2. If they are accelerating, there must be a force on them. What direction is the force? (Start with what is in contact with the object.) Towards the center Centripetal center seeking ∴What direction is the acceleration? towards the center (Always same as the direction of the force!) What would happen if the string broke?
- 2. Distance 2πr circumference Velocity 2π r tangent to the circle v= t Centripetal v2 towards the center a= acceleration r Centripetal Force Fc = mac towards the center 3 types of problems we’ll study Vehicle Spinning an Orbits object
- 3. Sample Problem On the swings at the Lake County Fairgrounds, passengers travel around a circle of radius 5 m in 4.0 s. a. What is aC? b. What is FC? (Use your mass) 2π r 2π 5 v= = = 7.85m / s T 4 2 2 v 7.85 a= = = 12.3m / s 2 r 5 F = ma = ( )12.0 = What is providing this center seeking force?
- 5. Sample problem 2 A car rounds a circular turn of radius 5 m. If the road is flat and the coefficient of friction between the tires and the road is 0.5, how fast can the car go without skidding? F = ma μ m g = m (v2/r) c c (0.5)(3200)(9.8) = (3200)(v2/5) FF = v = 4.95 m/s μ FN = Does it matter if it’s a μ Fg = Volvo or a semi? No!!! How m g = m the car go when the road is icy and the μ fast can (v /r) 2 coefficient of friction is 0.2? vicy = 3.13 m/s
Editor's Notes
- #2: tangential velocity a come off tangent to the circle Show the water bucket moving.