Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Work and Power
Document related concepts
Transcript
Work and Power CH 14.1 True False Statement Work is the product of force, distance and time Power is the amount of work done in a certain time Horsepower, is compared to an actual horse’s power The SI unit for work is the watt The SI unit for power is the joule True False Work Work is the product of force and distance Force is unbalanced Work Requires Motion Depends on Direction Some of the force must Forces act in the same act in the same direction as the object moves direction as the movement Force that does not act in the direction of motion does not do work on an object No movement = no work Calculating Work How much work is done SI Units W= J, joule F= d=m by a weight lifter who lifts 1600N over his head, at a height of 2m? Given: Formula: Solve: Power Power- rate of doing work Work at a faster rate = increasing power Increase power More work in a given time More work in less time Calculating Power You exert a force of 72N SI Units P= W, watt = 1J per s W= J t= s to lift a box to a height of 1m in 2s. How much power is used to lift the box? Give: Formula: Solve: Math Practice pg 415 1. 3. 2. Horsepower Horsepower hp = 746 watts James Watts Comparison of power outputs of steam engines vs output of strong horse Work and Machines CH. 14.2 True False Statement Machines make work easier, by changing force, direction or distance The force you exert on a machine is output force The final product of the machine is called output force Output work is always less than input force due to friction Both force input and force output are equal to force x distance True False Machines and Work Machine A device that changes force Make work easier by Changing size of force Direction of force Distance over which force acts Machines and Work Increasing Force Small force over a large distance = large force over a short distance Ex-jack Increasing Distance Decrease applied force by increasing the distance in which the force is exerted Changing Direction Ex-oar Work Input Input force force you exert on machine Input distance distance of input force Work Input input force x input distance Friction makes work done by a machine less than the work done on the machine Work Output Output force force exerted by the machine Output distance distance of output force Work Output output force x output distance Mechanical Advantage and Efficiency CH. 14.3 True False Statement Mechanical advantage is the # of times a machine increases output force IMA is the ideal mechanical advantage, which is only possibly without friction AMA is the actual mechanical advantage, which is output force/input force Efficiency of a machine is the input work that becomes output work Efficiency can never equal 100% True False Mechanical Advantage The # of times that a machine increases an input force Ex: Nut cracker At pivot- 7 times your input force At middle- 3 times your input force Mechanical Advantage Actual Ideal IMA is the mechanical •AMA is the actual forces acting on a machine advantage in the absence of friction Actual MA is always less than the IMA due to friction Calculating IMA IMA = Input Distance A woman drives her car Output Distance No SI Unit onto a ramp for repairs. She drives 1.8m along the ramp to raise the car 0.3m. What is the IMA? Given: Formula: Solve: Math Practice pg 425 1. 3. 2. Efficiency The % of work input that becomes work output Due to friction, it is always less than 100% Efficiency= Work Output Work Input X 100% Reduce friction = more efficiency Simple Machines CH 14.4 True False Statement Compound machines contain 2 or more of the 6 simple machines There are 4 classes of levers, that depend where the fulcrum is located A thin wedge has a bigger IMA than a thick wedge A wheel and axle, is composed of 1 wheel, or disk An inclined plane IMA is the height/ the distance True False Simple Machines 6 Simple Machines Lever A ridged bar, free to move around a fixed point Fixed point moves around a fulcrum IMA = input arm/output arm 1st Class MA = 1, < 1, > 1 2nd Class MA = > 1 3rd Class MA = < 1 Name the Lever Wheel and Axle 2 disks with different radii IMA = radius of input force/ radius of output force MA = > 1 Inclined Plane Slanted surface along which a force moves an object to difference elevation IMA = distance of inclined plane/ change in height Wedge V shape, with 2 inclined planes sloped into each other MA = > 1 Thin wedge of a given length has a greater IMA than a thick wedge of the same length Screw Inclined plane wrapped around a cylinder Closer threads have more IMA than far apart threads Pulley Rope that fits into a groove in a wheel IMA = # of rope sections supporting the load being lifted Fixed Pulley Rotate in place MA = 1 Movable Pulley Attached to the object being moved Pulley System Mix of fixed and movable Name the Pulley Compound Machines Combination of 2 or more simple machines working together Scissors Wedge, and lever Name the simple Machines http://www.rubegoldberg.com/
