Lecture05 - Newtons General Physics I Mechanics Racquetball...

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Unformatted text preview: Newtons General Physics I Mechanics Racquetball Striking a Wall Laws Physics 140 Mt. Etna Stewart Hall Kinematics and Dynamics Kinematics : How do we describe motion? Dynamics : Why does motion occur this way? Next three lectures : Dynamics why bodies move the way they do and what controls their motion Today : Newtons Laws, the foundation of classical mechanics This month : Keep ignoring possible rotations or oscillations and keep treating all moving bodies as particles (since every point moves exactly the same way as any other) Matter and Interactions All matter around us consists of atoms Each atom is comprised of a nucleus and electrons orbiting that nucleus Each nucleus is made of protons and eutrons neutrons Protons and neutrons are comprised of quarks (three quarks in each) Quarks and electrons are currently viewed as elementary particles , i.e. the most fundamental units of matter that do not have any structure (point particles) Matter and Interactions There are only 12 elementary particles in nature Particles of matter interact , i.e. act on one another There are four fundamental interactions in nature: Gravitational interaction lectromagnetic teraction Electromagnetic interaction Strong interaction Weak interaction Strong and weak interactions appear only at very tiny scales, less than the size of an atomic nucleus Gravity and electromagnetism are responsible for the bulk of interactions around us (studied in Physics 140 and Physics 240) What are Forces? In physics, force is a measure of interactions between two bodies Forces are vectors : have both magnitude and direction Forces on a given body are produced by other bodies acting upon it If you cannot identify another body producing a force on a given body, then there is no such force A body cannot act upon itself with a force Measured in Newtons (1 N = 1 kg m/s 2 ) You cannot pull yourself out of a swamp y simply NOT possible! by simply pulling your own hair up! Examples of Forces Pull (by a cord) Push (by a hand) Normal force (by a table) Friction (by a surface) Resistance (by a medium water or air) Elastic force (by a spring) Gravity (by Earth) Electric force (by electric charges) Magnetic force (by electric currents) Examples of Forces Pull (by a cord) Push (by a hand) Normal force (by a table) Friction (by a surface) These all are of electro- magnetic rigin Resistance (by a medium water or air)...
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Lecture05 - Newtons General Physics I Mechanics Racquetball...

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