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Ch 14 Work Power SM
Work, Power, and Simple Machines
Question | Answer |
---|---|
A grooved wheel with a rope, chain, or cable running along the groove. | Pulley |
An inclined plane with one or two sloping sides. It is used for prying or cutting. | Wedge |
A bar that is free to pivot or turn around a fixed point. | Lever |
A shaft or axle attached to the center of a larger wheel, so that the wheel and axle rotate together. | Wheel and Axle |
A sloping surface, such as a ramp that reduces the amount of force required. It is usually used for lifting up. | Inclined Plane |
A cylindrical shape with an inclined plane wrapped around it. | Screw |
Give an example of a compound machine. | Scissors, bicycle, etc. Anything that has 2 or more simple machines |
What class of lever is a broom? When you sweep with it the pivot is your shoulder, you push in the middle, and work is done at the end. | Third Class lever |
What class of lever are scissors? | First Class Lever |
What class of lever is a wheel barrow? | Second Class Lever |
What is the mechanical advantage of a machine? | It tells how much a machine multiplies your force. It is the ratio of output force/input force, or input distance/output distance. |
How do simple machines make work seem easier? | They change the force needed by the person using them, but NOT the work done. They can also change the distance, speed, or direction |
A device that does work with only one motion | simple machine |
A device that is made up of two or more simple machines | compound machine |
A push or pull | Force |
Force x distance | Work |
An object must do this for work to be done | MOVE in the direction of the force |
The rate of doing work, or work/time | Power |
SI Unit for Force | Newton (N) |
SI unit for Work | Joule (J) |
SI unit for Power | Watt (W) |
Si unit for time | second (s) |
SI unit for distance | meter (m) |
How are work and energy related | it takes energy to do work |
What is horsepower | the power of an average strong horse, English unit of power. |
The work a person does on a machine by moving it | input work |
the work a machine does on something else | output work |
Do machines do more work that the person does using them | NO. Output work is always a little smaller due to energy lost as heat or friction. They just make work seem easier by changing the force, distance, speed, or direction of work. |
The force a person pushes on a machine with | input force |
The force a machine pushes on something else with | output force |
The distance a person moves a machine | input distance |
The distance a machine moves something else | output force |
Do machines make less work? | NO! They make it seem easier by changing: force, distance, direction, or speed. But the work done is the same. |
Name the simple machine or machines in a wheel barrel | 2nd class lever and wheel and axle |
Name the simple machine or machines in a screw driver to pry open a paint can | 1st class lever and wedge |
Name the simple machine or machines in a pair of scissors | 1st class lever and wedge |
Name the simple machine or machines in a bike | wheel and axle (pedals, gears, and wheels), levers in kick stand, brakes, handle bars for steering |
Name the simple machine or machines in a flag pole or miniblinds | pulley |
Name the simple machine or machines in a steak knife | wedge |
Name the simple machine or machines in a soda bottle | screw (lid) |
Name the simple machine or machines in a hammer | wedge, first class lever pulling out a nail, third class lever hammering in a nail |
Name the simple machine or machines in a winding trail with switch backs (zig zag path) up a mountain | inclined plane |
Name the simple machine or machines in a pencil sharpener | wheel and axle and wedges inside for sharpening the pencil |
Name the simple machine or machines in a nut cracker | wedges and 2nd class lever (pivot on end, nut in middle, and you pull on other end) |
Name the simple machine or machines in a staple remover | wedges and 3rd class lever (pivot on end, you push in the middle, and staples removed at other end) |
What is the work done move a box 3 meters with 50 N of force | 150 Nm or 150 J |
What is the power required to move a box 3 m with 50 N of force if it takes 3 sec | 50 J/s or 50 W |
What is the IMA of a lever with an input arm of 11 cm and an output arm of 2 cm | 5.5 (no unit!) |
What is the AMA of a machine that has an input force of 50 N that produces an output force of 350 N? | 7 |
What is the efficiency of a machine that does 800 J of output work with 850 J of input work? | 94% |