* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Newton`s Laws/ Simple Machine Notes
Survey
Document related concepts
Faster-than-light wikipedia , lookup
Jerk (physics) wikipedia , lookup
Coriolis force wikipedia , lookup
Relativistic mechanics wikipedia , lookup
Seismometer wikipedia , lookup
Classical mechanics wikipedia , lookup
Rigid body dynamics wikipedia , lookup
Newton's theorem of revolving orbits wikipedia , lookup
Equations of motion wikipedia , lookup
Fictitious force wikipedia , lookup
Work (thermodynamics) wikipedia , lookup
Mass versus weight wikipedia , lookup
Centrifugal force wikipedia , lookup
Hunting oscillation wikipedia , lookup
Classical central-force problem wikipedia , lookup
Transcript
Describing Motion 3/23/2015 3:57:00 PM Motion- occurs when an object changes position relative to a reference point DISTANCE vs. DISPLACEMENT Distance – how far an object has traveled Displacement – distances and direction of an object’s change in position from starting point SPEED Speed – the distance an object travels per unit time – rate of change in position Avg. Speed (v) = total distance (d) / total time (t) V=d/t Type of speed Description Example INSTANTANEOUS Speed at any given point in time Driving a car and looking down at the speedometer AVERAGE Total distance traveled Taking a road trip divided by total time CONSTANT Speed that does not vary GRAPHING MOTION Putting car in cruise control Acceleration 3/23/2015 3:57:00 PM Velocity (v) – includes speed of an object and the direction of its motion Q: what is the difference between speed and velocity? A: Velocity includes directions where speed does NOT. Acceleration (a)- rate of change of velocity Acceleration occurs when an object changes speed, its direction, or both Calculating Acceleration Acceleration (meters/ seconds) = change in velocity (m/s) Time (s) note: change in velocity = final velocity – initial (starting) velocity Positive acceleration: The plane is speeding up. Negative acceleration: The bike is slowing down. Motion and Forces 3/23/2015 3:57:00 PM Force – a push or pull applied to an object Net Force – when two or more forces act on an object at the same time Friction- the force that opposes the sliding motion of two touching surfaces Type of Friction Description Example Static Friction in which two surfaces are not moving past each other Pushing a fridge across a floor Sliding Friction where two surfaces past one another Sledding down a hill Rolling Friction between a rolling object and surface it rolls on Skateboard moving on ground Fluid Friction when object moves through fluid, meaning either a liquid or a gas Skydiving Friction is caused by microscopic bumps on surfaces called microwelds. Air Resistance- friction- like force that opposes motion of objects that move through air – depends on speed, size, and shape of object Newton’s Laws of Motion 3/23/2015 3:57:00 PM Newton’s First Law of Motion An object in motion stays in motion, or an object at rest stays at rest until an unbalanced net force acts upon it Inertia: tendency of an object to resist any change in its motion Newton’s Second Law of Motion A net force acting on an object causes the object to accelerate in the direction of the force Force = mass times acceleration Newton’s Third Law of Motion For every action (or force), there is an equal and opposite reaction (or force) Momentum- property of a moving objecting resulting from its mass and velocity Momentum (p) = mass times velocity Gravity 3/23/2015 3:57:00 PM Gravity – any two masses that exert an attractive force on each other Gravity depends on mass and distance between objects Weight – gravitational force exerted on an object; measured in units called Newtons The greater the objects mass, the stronger the gravitational force on it Projectile Motion Projectile – anything that is thrown or shot through air A projectile follow a curved path and has: Horizontal Motion and Vertical Motion Motion parallel to Earth’s Surface Motion perpendicular to Earth Centripetal Force Centripetal acceleration – acceleration toward the center of a curved or circular path “Centripetal” means toward the center Centripetal Force – force acting toward the center of a curved or circular path The Nature of Energy 3/23/2015 3:57:00 PM Energy – the ability to cause change Forms of energy include: - Electrical - Thermal (heat) - Chemical - Radiant (light) Kinetic Energy – energy in the form of motion KE depends on mass and velocity of moving object. Example of KE: Going down a slide Potential Energy – energy that is stored Example of PE: waiting at top of slide Elastic Potential Energy- energy stored by something that can stretch or compress, such as a rubber band or a spring Chemical Potential Energy- energy stored in chemical bonds A glass of milk has CPE until you drink it then calories are used as energy for your body Gravitational Potential Energy- anything that can fall has stored GPE A ball on a ledge has GPE Conservation of Energy 3/23/2015 3:57:00 PM Energy can be transformed from one form to another Ex. Light Bulb Light energy Thermal energy Mechanical Energy – total amount of kinetic energy and potential energy in a system ME= PE + KE Point A: PE Maximum, KE = 0 Point B: KE , PE Point C: KE , PE Point D: PE Maximum, KE = 0 * : Total Mechanical Energy The Law of Conservation of Energy- Energy may change form, but it cannot be created nor destroyed in ordinary conditions Work 3/23/2015 3:57:00 PM Work – transfer of energy that occurs when a force makes an object move For work to be done, something has to move AND the motion must be in the same direction as the force. When work is done, a transfer of energy always occurs. Calculating Work: Work (Joules) = Force (Newtons) times Distance (meters) W= F * D Ex. You push a wheelbarrow with a force of 100N. You moved the wheelbarrow 5m. How much work did you do? W= F * D W= (100N) * (5m) W= 500 J Power- the rate at which work is done. Calculating Power: Power (Watts) = work (J) Power equals work divided by time Time (s) Ex. You do 900J of work pushing a fridge. It took 5 seconds. What was your power? P = W/T = 900J/ 5s = 180 J/s = 180 watts (w) Work: transfer of energy that occurs when a force makes an object move Unit: Joules W (J) = F x D Distance: the distance an object moves from one place another D (m) = W/F Unit: Meter Force: Push or pull Unit: Newtons F (N) = W/D Using Machines 3/23/2015 3:57:00 PM Machine – device that makes doing work easier Machines make work easier by easing the force that can be applied to an object Two force are involved when a machine does work (Fin) Input Force the force applied to machine Output Force (Fout) the force applied by machine Picture of Hammer Mechanical Advantage – the ratio of the output force to the input force Mechanical Advantage (MA) = Output force (Newtons) Input force (Newtons) MA = Fout Fin Efficiency- measure of how much work put into a machine is changed into useful work by the machine Machines can be made more efficient by reducing friction. Increasing Force: Machines can make work easier by increasing the force that can be applied to an object Increasing Distance: Machines can make work easier by increasing the distance over which a force is applied Changing Direction: Machines can make work easier by changing the direction of an applied force Simple Machines 3/23/2015 3:57:00 PM Simple Machine – Machine that does work with only one movement of the machine Lever: Bar that is free to pivot around a fixed point (fulcrum) Pulley Grooved wheel with a rope chain or cable running along groove 1st Class Lever: fulcrum is between input Fixed Pulley: attached to something that force and output force doesn’t move (directional advantage) 2 Moveable Pulley: one end of the rope is nd Class Lever: output force(Load) is between fulcrum and input force fixed and the wheel is free to moved 3 (mechanical advantage) rd Class Lever: input force (Effort) is between fulcrum and output force Block and Tackle: system of pulleys consisting of fixed and moveable pulley Wheel and Axle: Consists of an axle attached to center of a larger wheel so that the wheel and axle rotate together Inclined Plane: Sloping surface, such as a ramp that reduces the amount of force required to do work The Screw: Inclined plane wrapped around a cylindrical post The Wedge: An inclined plane with one or two sloping sides (Knife) Compound Machine: Two or more simple machines that operate together 3/23/2015 3:57:00 PM 3/23/2015 3:57:00 PM 3/23/2015 3:57:00 PM