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Science Gr. 8 Ch. 14
2015
| Question | Answer |
|---|---|
| All cars come with ______& ______ designed to make changing a tire a fairly easy task. | |
| What are 2 simple machines used in changing a tire? | a lug wrench and jack |
| What is a device that changes a force? | a machine |
| Machines make work ____________ to do | easier |
| Machines change the _________of the force needed, the __________of a force, or the ______over which a force acts. | size, direction, distance |
| Turning a jack handle allows a man to raise a car. The distance moved by the handle if much ____________ than the distance the car is raised. | greater |
| Each complete rotation of the jack handle applies a small force over a large ______________. | distance |
| Each rotation that a jack handle is turned lifts a car only a very short ____________. | distance |
| A small force exerted over a large _____________ becomes a large force over a short _______________. | distance, distance |
| If a machine increases the distance over which you exert a force, then it decreases the amount of _________ you need to exert. | force |
| Some machines _________________ the applied force but _______________ the distance over which the force is exerted. | decrease, increase |
| A machine that decreases the distance through which you exert a force ______________ the amount of force required. | increases |
| Pulling back on the handle of an oar causes its other end to move in the ___________ direction. | opposite |
| Because of ________________, the work done by a machine is always _______________ than the work done on the machine. | friction, less |
| What is the force you exert on a machine called? | input force |
| What is the distance the input force acts through called? | input distance |
| What is the work done by the input force acting through the input distance called? | work input |
| What is the input force multiplied by the input distance? | work input |
| For an oar, what is the input force? | the force exerted on the handle |
| For an oar, what is the input distance? | the distance the handle moves |
| What are 2 ways to increase the work input of an oar? | 1. Increase the input distance. 2. Increase the input force. |
| What is the force exerted by a machine called? | output force |
| What is the distance the output force is exerted through? | output distance |
| What is the output force multiplied by the output distance? | Work output |
| In the case of an oar, why is the output work less than the input work? | friction |
| What do machines use to overcome friction? | some amount of input work |
| What is the only way to increase the work output? | Increase the amount of work you put into the machine. |
| You do 200 J of work pulling the oars of a rowboat. What can you say about the amount of work the oars do to move the boat? | Less than the 200 J of work are done to move the boat because some of the input work is lost to friction forces. |
| How can you increase the work output of a machine? | By doing more work |
| An advertisement for a new type of wrench claims it reduces the force needed to tighten a bolt. If the advertisement is correct, what do you know to be true about the input distance? | It is increased |
Created by:
dsibley