1989 words - 8 pages

Projectile Motion*Object, moving in gravitational field, with gravity only force acting on it - moves in a parabolic shape*Measured in two independent dimensionsoVertical - gravity effectsoHorizontal - remains constant though-out motion*Galileo - formulas for projectile motionoS = UT - Horizontal motionoS = UT + ½ AT2 - Vertical motionGalileo analysis of Projectile motion*Trajectory of projectile makes a parabolic shape*Led him to consider reference frames*Opponent believed in idea of geocentrism - stone would be left behind if Heliocentric*Galileo explained - didn't fall away because shared the earths motionoTower and stone shared the same horizontal velocityoExperiment - dropped object from crows nest of ship - dropped down to base of tower whether stationary or moving at a constant velocity*This led to Galilean relativityo'The laws of mechanics are the same in a frame of reference that is at rest or one that is moving at a constant velocity'Escape Velocity*The necessary velocity needed to leave the earths surface*Depends on gravitational acceleration of planet - hence mass and diameter of planet*~11.2 km/sec on earth - not taking into account atmospheric friction*Lower escape velocity - least likely planet has atmosphereNewton and Escape Velocity*Proposed the idea of artificial satellites*Projectile launched horizontally from mountain -oAs launch velocity increased, object would go further till crashing or till it follows ellipse of earth - orbitCircular motion*Motion of an object in circular path, with constant speed - uniform circular motion*Speed same - however changing velocity and accelerating - direction always changing*Change in velocity - directed towards centre of circle; centripetal force*Uniform circular motion - centripetal force is always towards centre of circle*Ac = MV2/R*Orbit is acquired by lifting a satellite and giving it require horizontal velocityG-Forces - Relationship with Astronauts*Can experience g-forces up to ~10 g*Acceleration - right angles to long axis*Therefore inclined in mounded seats - force directed towards back*Dip of a roller-coaster - positive g-forces experienced (feels heavier) - force acting up to counter this + centripetal force to centre*Similar to g-forces experienced by astronautsImpact of Earth's orbital motion and rotational orbit - relationship with the launch of a rocket*As rocket rises - tilted east to take advantage of earths rotation*Rocket will already have speed of earth's rotation - 400m/sec at Cape Canaveral*Rocket travelling to planets - take advantage of earths orbit around sunoLaunched in direction of earth's orbit for outer planets (has 30 000m/s) increase velocity increase orbit around sunoInner planets - launched opposite direction to earth orbit around sun; decrease velocity around sun, enters elliptical orbitChanging acceleration of rocket in terms of*Laws of conservation of momentumoRocket moves in one direction, equals force produced by expelling gasoExpelled gases carry...

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