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Roller Coaster Physics Energy and Work Newton’s 1st Law • An object in motion stays in motion in a straight line, unless acted on by an unbalanced force. • In a roller coaster, the riders want to continue moving in a straight line due to their inertia. • The coaster track and car apply the unbalanced forces to the riders, which makes it fun! Roller Coasters and Gs Roller Coasters and Energy • Roller coaster cars have no motors. • There usually is a large hill at the beginning of the ride. • As the cars travel up the hill, they gain energy. • Potential Energy ▫ Energy of position ▫ Stored energy Roller Coasters and Energy • After the roller coaster reaches the top of the hill, the force of gravity pulls it downward. • As gravity accelerates the car, its velocity increases. • Kinetic Energy ▫ Energy of motion Roller Coasters and Energy Energy and Work Energy is the ability to do WORK. • Work is measured in a formula: • Work = force x distance • W=F x d • Where: ▫ Force, measured as Newtons (N) ▫ Distance, measured as meters (m) ▫ Work, measured as Newton x meter = Joule (J) ▫ So Joules (J) is the unit of measure for both work and energy! Work example problem: • How much work is done when we push with a force of 75 N to move a bookcase a distance of 2 meters? • Work = force x distance • W = 75 N x 2 m • W = 150 N x m or • W = 150 J Potential Energy • (Gravitational)Potential Energy Formula: PE = weight x height (remember: weight = mass x gravity) • Where: ▫ PE = Potential Energy, measured in Joules (J) ▫ W = weight, measured in Newtons (N) ▫ h = height, measured in meters (m) Potential Energy Example A roller coaster car with a weight of 980 newtons is pulled up a hill to a height of 40 meters. How much potential energy did the car gain? PE = w x h PE = (980 N)(40 m) PE = 39,200 J Kinetic Energy • Kinetic Energy Formula: KE = ½ m x v2 This is the same as KE = mv2 2 ▫ KE = Kinetic Energy, measured in Joules (J) ▫ m = mass, measured in kilograms (kg) ▫ v = velocity, measured in meters per second (m/s) Kinetic Energy Example At the bottom of a hill, a roller coaster car with a mass of 100 kg is traveling with a velocity of 28 m/s. What is the kinetic energy of the car? KE = ½ m v2 KE = ½ (100 kg) (28 m/s)2 KE = ½ (100 kg) (784 m2/s2) KE = 39,200 J Law of Conservation of Energy • Energy is not created or destroyed, it only changes forms. Roller coaster examples: • Energy from a motor is used to pull the cars uphill. That energy is converted to potential energy. • As the cars travel downhill and speed up, potential energy is changed into kinetic energy. • During the ride, the tracks heat up due to rolling friction. Kinetic energy is changed into heat energy. Energy and Work • Energy is the ability to do work. • Work is applying a force over a distance. • Formula for Work: W=Fxd Where: • W = Work, measured in Joules (J) • F = Force, measured in Newtons (N) • d = distance, measured in meters (m) Roller Coaster Physics