Ch 4 notes
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This 4 page Class Notes was uploaded by Alikhan Ladhani on Sunday February 21, 2016. The Class Notes belongs to Astr 1010 at Georgia State University taught by in Spring 2016. Since its upload, it has received 53 views. For similar materials see Astronomy in Science at Georgia State University.
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Date Created: 02/21/16
CH 4 Making sense of the universe: Understanding the Motion , Energy and Gravity 02/15/2016 How do we describe motion? Speed- rate at which object moves speed= distnac(unitsofm ) o time s o ex. Speed of 10 m/s velocity- speed and direction ex. 10 m/s due east acceleration- any change in velocity units of speed/ time (m/s ) 2 the acceleration of gravity falling objects accelerate at the same rate (not counting friction of air resistance) g= 10 m/s : speed increases 10m/s with each second of falling Galileo proved that all objects fall at the same speed regardless of mass ex. a ball will fall at the same g as an elephant at the same height Momentum and Force Momentum= mass x velovcity Net force changes momentum which generally means an acceleration Rotational momentum of a spinning or orbiting object is know as angular momentum Is there a Net Force? 1. A car coming to a stop. Y 2. A bus speeding up. Y 3. An elevator moving up at constant speed. N 4. A bicycle going around a curve. Y 5. A moon orbiting Jupiter. Y Mass different from Weight Mass- amount of matter in an object Weight- force that acts upon an object o You are weightless in free fall Astronauts weightless in space There is gravity in space Weightlessness is due to a constant state of free- fall Newtons Three Laws of Motions First law: object moves at constant velocity unless a net force acts to change its speed or direction (an object in motion stays in motion unless acted by an outside force) Second law: Force = Mass x Acceleration Third law: for every force there is always an equal and opposite reaction force Conservation of Momentum The total momentum of interacting objects cannot change unless an external force is acting on them Interacting objects exchange momentum through equal and opposite forces … example: pool balls Conservation of Angular Momentum Angular momentum= mass X velocity X radius The angular momentum of an object cannot change unless an external twisting force (torque) is acting on it Earth experiences no torque as it orbits the Sun, so its rotation and orbit will continue indefinitely the conservation of momentum explains why objects rotate faster as they shrink in radius energy makes matter move energy is conserved but it can transfer from one object to another change in form energy can change type but cannot be destroyed Basic types of energy Kinetic (motion) Radiative(light) Stored or potential o Gasoline o Battery Conservation of energy Energy can be neither created nor destroyed It can change form or be exchanged between objects The total energy content of the universe was determined in the big bang and remains the same today Thermal Energy: the collective kinetic energy of many particles Thermal energy is a measure of the total kinetic energy of all the particles in a substance. It depends on temperature AND density Temperature is the average kinetic energy of the many particles in a substance. In low temp particles move slowly and in high temp particles move faster Temperature scale Absolute zero= 0 K, -273.15 C, -459.67 F Water freezes= 273.15 K, 0 C, 32 F Water boils= 373.15 K, 100 C, 212 F C to K= +273.15 Gravitational potential energy On earth depends on Mass of object (m) Strength of gravity (g) Distance object could potentially fall In space, an object or gas cloud has more gravitational energy when it is spread out than when it contracts. A contracting cloud converts gravitational potential energy to thermal energy. What determines the Strength of Gravity Universal law of Gravitation 1. Every mass attracts every other mass. 2. Attraction is directly proportional to the product of their masses. 3. Attraction is inversely proportional to the square of the distance between their centers.
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