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Centripetal Force and Gravity. 4/27/07. Recap. v 2. s. a c =. s = r . =. r. r. a c = r 2. v T = r . . 2. =. =. v 2. t. T. F c = ma c = m. r. a T = r . . =. F c = ma c = mr 2. t. Recap (UCM). Uniform Circular Motion.
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Centripetal Force and Gravity 4/27/07
Recap v2 s ac = s = r = r r ac = r2 vT = r 2 = = v2 t T Fc = mac = m r aT = r = Fc = mac = mr2 t
Recap (UCM) Uniform Circular Motion UCM means that is constant Which means that… = 0 aT = 0 |vT| = constant BUT… vT is not constant because the direction changes
UCM FSB
UCM FSB
UCM FSB FSB
UCM FSB FSB
UCM FSB FSB FSB
UCM FSB FSB FSB
UCM FSB FSB FSB FSB
Vertical UCM FSB
Vertical UCM mg FSB What’s keeping the ball pinned up against the top?
Vertical UCM mg FSB What’s keeping the ball pinned up against the top? Inertia
Vertical UCM Fc is the sum of the inward forces on the ball. mg FSB Fc Fc = F = FSB + mg
Vertical UCM Fc is the sum of the inward forces on the ball. v2 Fc = mr2 = m r mg FSB Fc Fc = F = FSB + mg
Vertical UCM Fc is the sum of the inward forces on the ball. v2 Fc = mr2 = m r mg FSB v2 m = FSB + mg r Fc Fc = F = FSB + mg
Vertical UCM Fc is the sum of the inward forces on the ball. FSB mg
Vertical UCM Fc is the sum of the inward forces on the ball. FSB mg Fc = F = …
Vertical UCM Fc is the sum of the inward forces on the ball. FSB mg Fc = F = FSB
Vertical UCM FSB
Vertical UCM FSB mg
Vertical UCM Fc is the sum of the inward forces on the ball. Fc = F = FSB mg
Vertical UCM Fc is the sum of the inward forces on the ball. Fc = F = FSB FSB mg
Vertical UCM Fc is the sum of the inward forces on the ball. Fc = F = FSB - mg FSB mg
Vertical UCM Fc is the sum of the inward forces on the ball. Fc = F = FSB - mg v2 Fc = mr2 = m FSB r v2 m = FSB - mg r mg
Vertical UCM Is the force of the string on the ball greater at the top or at the bottom?
Vertical UCM mg Is the force of the string on the ball greater at the top or at the bottom? FSB FSB mg
Vertical UCM What is the slowest vT the ball can have if it doesn’t fall when it reaches the top?
Vertical UCM Happens when Fc just counters mg (I.e. FSB = 0) What is the slowest vT the ball can have if it doesn’t fall when it reaches the top?
Vertical UCM Happens when Fc just counters mg (I.e. FSB = 0) What is the slowest vT the ball can have if it doesn’t fall when it reaches the top? v2 m = mg r
Vertical UCM Happens when Fc just counters mg (I.e. FSB = 0) What is the slowest vT the ball can have if it doesn’t fall when it reaches the top? v2 m = mg r v2 = g r
Vertical UCM Happens when Fc just counters mg (I.e. FSB = 0) What is the slowest vT the ball can have if it doesn’t fall when it reaches the top? v2 m = mg r v2 = g r v2 = rg
Vertical UCM Happens when Fc just counters mg (I.e. FSB = 0) What is the slowest vT the ball can have if it doesn’t fall when it reaches the top? v2 m = mg r v2 = g r v2 = rg v = rg