Science Chapter 4 - Lesson 3 (Simple Machines)
What is the MA of pulleys?
MA = number of sections of rope pulling up on object
What is a pulley system made up of?
combination of fixed and movable pulleys that work together
Two or more gears working together form a ___________ machine.
compound
Moveable pulleys ________ the force needed to lift and object while the _____________ over which the force acts increases.
decrease distance
Each simple machine _____________ the overall efficiency of the compound machine.
decreases
The shape of the wedge gives the output forces a different __________ than the output force.
direction
First-class levers: If the MA is less than 1, the input arm is _________ than the output arm. And the output force is _______________ than the input force.
shorter less
For third-class levers, the input arm is always ____________ than the output arm. The MA of third-class lever is always ______________ than 1.
shorter less
Gears of different sizes turn at different ____________.
speeds
What is a screw?
An inclined plane wrapped around a cylinder
The __________________ built pyramids using huge stone blocks and inclined planes to make moving easier.
Ancient Egyptians
Why are front teeth wedges?
As you push front teeth into food, the downward force is changed by your teeth into a sideways force that pushes the food apart.
What is formula for Ideal Mechanical Advantage (IMA)?
IMA = length of input arm/length of output arm measured in meters IMA = L(in)/L(out)
IMA of Wheel and Axle
IMA = radius of wheel/radius of axis measured in meters IMA = F(wheel)/F(axle)
The human body uses all three classes of levers to move. ________________ provide the input force for the levers.
Muscles
How do you measure the efficiency of a compound machine?
You multiply the efficiencies of each simple machine together; Example - Can Opener: Efficiency of lever = 95% Efficiency of wheel & axle = 90% Efficiency of wedge = 80% Can opener efficiency = 95% x 90% x 80% = 68%
How does a screwdriver make work easier?
You have a small input force with a large input distance, so when the machine increases force, it results large output force with a small output distance.
What is an inclined plane?
a flat, sloped surface
What is a pulley?
a simple machine made of a grooved wheel with a rope or cable wrapped around it
What is a lever?
a simple machine made up of a bar that pivots, or rotates, about a fixed point
What is a wedge?
a sloped surface that moves; can have one or two sloping sides; (ex: doorstop - wedge with 1 slope; axe - wedge with 2 slopes)
What is a fixed pulley?
a wheel attached in a fixed location a FIXED PULLEY only changes DIRECTION of force
First-class levers: If the MA is equal to 1, the input arm is _________ to the output arm. And the output force is _______________ to the input force.
equal equal
Smaller gears rotate ________ than larger gears.
faster
The amount of ________ transmitted through a set of gears is also affected by the size of the gears.
force
first class lever
fulcrum in the middle of input and output force Examples - hammer pulling nail from wood; finger tab on a beverage can
__________________ the length and _____________ the height of an inclined plane increases its ideal mechanical advantage (IMA).
increasing decreasing MA = length/height
When you turn a screw, the screw threads change the _____________ force to a(n) ____________ force.
input output
The distance from the fulcrum to the input force on the tab is called the _____________________.
input arm
It takes __________ force to move an object upward along an inclined plane than it does to lift the object straight up.
less
In first class levers, the ________________ of the fulcrum determines the mechanical advantage.
location
First-class levers: If the MA is greater than 1, the input arm is _________ than the output arm. And the output force is _______________ than the input force.
longer greater
The input arm is ____________ than the output arm for all second- class levers. The MA of a second-class lever is always ________ than 1.
longer greater Ex: wheelbarrow, nutcracker, foot
The input and output force act on ________________ ends.
opposite
The ___________ force pulls the screw into the material.
output
The distance from the fulcrum to the end of the tab is called the _____________________.
output arm
The input force applied to a large gear is _________ when it is applied to a small gear.
reduced; decreased
What is a moveable pulley?
when you attach a pulley to the object you wish to move.
What is an example of a fixed pulley?
window blind; flagpole
What is a fulcrum?
the pivot point of a lever
How many types of levers are there?
3 (first, second and third class levers)
What is a gear?
A gear is a wheel and axle with teeth around the wheel.
What is a compound machine?
A machine made up of two or more simple machines Ex: can opener
What is a simple machine?
A machine that does work with only one movement
third class lever
Input force is between output force and fulcrum, the output force is LESS THAN the input force Examples: tweezers, rake and broom
What is a wheel and axle?
It's an axle attached to the center of a wheel and both rotate together. (ex: screwdriver)
What are the 6 types of simple machines?
Lever Wheel and axle Inclined plane Wedge Screw Pulley
What is the MA of an inclined plane?
MA = length/height MA = l/h
Your ____________ acts like a first-class lever. Your ____________ acts like a second-class lever. Your ___________ acts like a third-class lever.
Neck (fulcrum is joint connecting skull to spine) Foot (fulcrum is the ball of your foot) Arm (fulcrum is elbow)
second class lever
Output force is between input force and fulcrum the output force is GREATER THAN input force Examples: wheelbarrow, nutcracker, & your foot
How many types of simple machines are there?
Six
True or False: A doorknob is a simple machine.
True. A doorknob is a wheel and axle type of simple machine.