Chapter 4 Flashcards
What is the formula for power
Work divided time
What is the formula for work
Force times distance
What is power measured
Watts
What is force measured
Joules
What is the definition of work
When a force causes an object to move in the direction of the force
Is pushing as stalled car work. Why
No because the cat isnt moving
If you pick a suitcase up and move forward is it work? Why?
No because the suitcase isn’t going in the same direction as the force
Where r u doing more work
1) lifting a 80N barbell
2) lifting a 160N barbell
You don’t know until you know how high each one is lifted
What is the definiton of power
Rate at which work is done
Machine defition
Device that makes work easier by changing the size and direction
Input force
The force you apply
Output force
The work the machine applies
Can work out put ever be greater then work input
No
What is mechanical advantage
How many times a machine multiplies your force
Do machines save work
No
What do machines change
Size of force and distance
With a machine increases the force what happens to the distance
It decreases
When machines change the direction of the force what is the mechanical advantage
1
What is the mechanical advantage of a machine that has a greater input force
Less than 1
Why is work output of a machine always less then the work input
Because if friction so the machine loses work
Mechanical efficency
Comparison of machines work output with the work input
What is the equation for mechanical efficiency
Work output divided by work input times hundred
Ideal machine
A machine with 100 percent efficency
What are the six simple machine
Lever, incline plane, wedge, screw, wheel and axle, and pulley
Lever
Simple machine consisting of a bar that pivots at a fixed point called a fulcrum
What are levers used for
Apply force to the load
First class lever
The fulcrum is between the input force and the load
What do first class levers fo
Change the direction of the input force
List one example of a first class lever
Teeter totter
Second class lever
Load is between the fulcrum and input force
How do second class levers help
Allow you to apply less force then the force exerted by the load
Third class lever
The input force is between the fulcrum and load
What do third class levers do
They don’t increase input force
Mechanical advantage of a first class lever
Greater then one
Whatis the mechanical advantage of a second-class lever
Greater than one
What is the mechanical advantage of a third class lever
Less than one
Incline plane
A straight slanted surface
How are inclined planes helpful
requires a smaller input force
What happens the distance with an inclined plane
The distance increases
Mechanical advantage of incline plane
The longer the inclined plane is compared with its height the greater the mechanical advantage
How do you calculate the mechanical advantage of an inclined plane
Divided length by height
wedge
Double inclined plane that moves
How are wedges helpful
Which is applying an output force that is greater then your input force
What happens to the distance with the wedge
It increases
Example of wedge
Knife
Mechanical advantage of wedge
The longer and thinner the wedge is the greater the mechanical advantage
How do you calculate the mechanical advantage of the wedge
Length divided by thickness
Screw
Incline plane wrapped in a spiral
Mechanical advantage of screwa
The longer the incline plane the greater the mechanical advantage and when u straighten it out it is a really long incline plane
Wheel and axle
Simple machine consisting of two circular objects of two different sizes
What is bigger wheel or axle
Wheel
Mechanical advantage if wheel and axle
Can be determined by dividing the radius of the wheel by the radius of the axle and turning the wheel makes a mechanical advantage of greater than one
Pulley
Grooved wheel that holds a rope or a cable
Fix pulley
Doesnt increase force
Movable pulley
Doesn’t change forces direction and you have to make both sides move
Block and tackles
Fixed pulley and moveable pulley together can have large mechanical advantage when several pulleys are used
Compound machines
Made of two or more compound machines
Some examples of compound machines
Block and tackle, scissors, and zipper
Mechanical efficiency of a compound machine
Mechanical efficiency of compound machine is low because the more moving parts a machine has the less mechanical efficiency and friction should be reduced as much as possible
