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# Download Motion Unit Class Notes

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Transcript

Motion Unit Class Notes Motion – a change in position; an object is in motion when its distance from another object (reference point) is changing Speed – the rate at which an object is moving Speed = Distance Time Speed = Distance ÷ Time Constant speed – same speed all the time Average speed – speed for a complete trip Instantaneous speed – speed at any one instant in time Velocity – speed in a certain direction Acceleration – rate at which velocity changes; either a change in speed or direction, or both Increase in speed Decrease in speed (deceleration) Change in direction Acceleration = Final velocity – Start velocity (change in velocity) Time (change in time) Newton’s Laws of Motion 1. An object at rest will remain at rest, and an object in motion will remain in motion unless acted upon by an outside force Force – a transfer of energy; a push or pull that starts, stops or changes the direction of an object Friction – force that happens when the surfaces of matter move past each other (Static, sliding, rolling, fluid) - depends on the surfaces and the force pushing them together Gravity – force that pulls objects towards each other - depends on the mass of the objects and the distance between them Inertia – an object’s tendency to keep doing what it is doing (rest or motion) - resistance to change - the greater the mass of an object, the greater its inertia 2. The net force on an object is equal to the product of its mass and its acceleration Force = Mass x Acceleration Newton = kg x m/sec2 3. When one object exerts a force on a second object, then the second object exerts a force of equal strength on the first object. - action/reaction law - not like balanced net force on 1 object, these action/reaction forces act on two different objects Momentum – a measure of an object’s inertia of motion Momentum = Mass x Velocity Law of Conservation of Momentum – the total momentum of objects that interact does not change, unless acted on by an outside force Energy – the ability to do work or cause change 1. Kinetic energy (KE) – the energy of motion - affected by mass and velocity 2. Potential energy (PE) – stored energy - has the potential to do work or cause change - position - ex. Gravity or Elastic potential energy - sun’s energy – ex. food, wood, fossil fuels Law of Conservation of Matter and Energy - energy cannot be created or destroyed, it only changes form - KE ↔ PE Work – changing the energy of an object Work = Force x Distance (moved in the direction of the force) Joule = Newton x meter Examples: Power – rate at which work is done Power = work ÷ time Watt = Joules ÷ seconds 1 horsepower = 746 watts Machine – a tool that makes work easier by…… 1. changing the size of the force applied - less force over a greater distance (ex. wheelbarrow) - greater force over a smaller distance (ex. hammer) 2. changing the direction of the force applied (ex. pulley) Work in = Work out Mechanical Advantage (MA) – how many times the machine multiplies force Types of machines 1. Lever – bar that pivots at a fixed point called a fulcrum 2. Wheel and axle – 3. Pulley – can be fixed or movable 4. Inclined plane 5. Wedge – an inclined plane that moves 6. Screw – an inclined plane wrapped around a cylinder to form a spiral