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Ch 8 Pg 131 Circular Motion. Rotational speed – RPM, angular speed T = time for 1 rev F = # rev per second, Hz (also called “period”) 1/T = F 1/F = T Tangential speed v = 2 π r T higher radius higher tangential speed
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Ch 8 Pg 131Circular Motion • Rotational speed – RPM, angular speed T = time for 1 rev F = # rev per second, Hz (also called “period”) 1/T = F 1/F = T • Tangential speed v = 2 π r T higher radius higher tangential speed ex: band turning corner, race track
Rotational inertia – more mass farther from center = harder to turn Pg 134,135 ex: gymnasts flipping skaters spinning more rotational inertia = more resistance Pg 136 hoop and hammer
Torque – force rotating around fulcrum, Pg 138 check T = F x D • Center of gravity – Pg 142 stable when located over base, pregnant women lean back, heavy backpacks cause you to lean fwd, demo Pg 155 #4,5
Centripetal force – Pg 144 pulls to center Fc = mac ( cent acc = v 2 ) r • Centrifugal force – apparent force of inertia leaving center, no real force simulated gravity in future?? Pg 149
Angular momentumL = mvr • Conservation of momentum – bigger or farther means slower (inversely prop) Pg 152 • Pg 156 Calc #5 & 6 in notebook
Satellites stay in orbit because centripetal force of gravity and forward force of inertia combine to = net force of zero if speed is fast enough (app 8 km/s Pg 194**) (curved path matches curve of Earth Pg 192**– we say it’s in freefall because it is falling below straight line path of inertia)
Ch 10 Pg 184Projectiles • Vertical falls from rest dy = ½ g t 2 Pg 188 (if any initial vel add product of that vel and total time) • Horizontal “falls” (throws) dx = vt (speed = d/t) Pg 190-91
Projectile parabolas – fireworks, kicking football higher angle = higher altitude lower angle = longer distance Pg 189 Projectile handout • Escape speed needed by PROBES Pg 200-203 (satellites don’t want to escape gravity) • Kepler and Elliptical Orbits Pg 197-99