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.