Compound Machines

Basic science rev questions for MTT

SIMPLE MACHINES

• A machine is an object that enables us to do work (task) easier and faster with minimum force (or effort).

• A machine may be simple or complex (compound).

• Compound/Complex machines are machines made up of two or more simple machines that work together in a coordinated way.

• Simple machines are objects/tools which uses applied force (input force) at one point called effort to overcome another force (resistance force) called load at some other point.

ADVANTAGES (CHARACTERISTICS) OF SIMPLE MACHINES

• It enables a large load to be overcome by a small effort.

• It enables us to do work more easily and faster.

• It enables us to work with less time and energy.

• It is small and easy to carry/use.

• It is readily available and in expense to purchase.

How does it operate (principle)?

• changing the direction of the input force exerted on the effort and

• increasing (multiplies) the output force exerted on the load needed to do work (task).

Multiple Choice

Simple machines make the work we have to do easier, but it is still the same amount of work.

• True

• False

Multiple Choice

What is anything that makes work easier called?

• screw

• wedge

• force

• machine

Multiple Choice

Simple machines can make work easier by reducing the input force needed to move an object. However, there is a trade off for decreased input. What is the trade off?

• The distance the object is moved is increased.

• The distance the object is moved is decreased.

• The amount of work is increased.

• The amount of work is decreased.

Two of the basic simple machines from which all the others are made are;

1. The lever

2. The inclined plane.

Other forms of simple machines are;

3. The pulley.

4. Wheel and axle

5. Wedges

6. Screws

7. Gears

All these machines generally constitute of three parts;

• Effort

• Load

• Fulcrum / pivot

The Effort: it is the point where the force is applied.

The Load: it is the point where the resistance force (weight) is overcome.

The Fulcrum: it is the point of balance or support, also called the pivot or turning point, or joining point between the load and effort.

Multiple Choice

WHAT ARE THE 3 MAIN PARTS OF A LEVER?

• FOOT, EFFORT, REPORT

• FULCRUM, STRUCTURE, EFFORT

• FULCRUM, EFFORT, LOAD

Multiple Choice

Which of the following is true for the picture?

• elephant is the fulcrum, mouse is the effort, triangle is the load

• mouse is the fulcrum, triangle is the effort, elephant is the load

• triangle is the fulcrum, mouse is the effort, elephant is the load

Multiple Choice

An object being lifted or moved is a

• load

• force

• fulcrum

• work

Multiple Choice

________________ is done whenever a force moves an object a distance

• load

• force

• friction

• work

LEVER

A lever is a solid bar or rod that rests on a fixed support called a fulcrum.

• The Effort: it is the point where the force is applied.

• The Load: it is the point where the resistance force (weight) is

  overcome.

• The Fulcrum: it is the point of balance or support, also called the pivot or

  turning point, or joining point between the load and effort.

How does it operate (principle)?

• It operates by decreasing or increasing the force (input force) exerted on one end (the effort) and multiplies or increases the force (output force) on the other end in order to do work.

• By exerting a force on one end of the lever, a force at the other end of the lever is created.

• The input (applied) force is either increased or decreased, depending on the distance from the fulcrum to the load, and from the fulcrum to the effort.

When the distance from the fulcrum to the load is long, the applied force on the effort is increased.

While

When the distance from the fulcrum to the load is short, the applied

force on the effort is decreased

First class lever

The fulcrum is between the load and effort

Second Class Levers

The load is between the effort and fulcrum

Third class lever

The effort is between the fulcrum and load

Applications of a Lever

It is used to push, pull, or lift things called load at a straight angle. Force is required for lever to do work.

Multiple Choice

• 1st Class
• 2nd Class
• 3rd Class
• It is not a lever

Multiple Choice

How can the lever be balanced

• add weight to the right side

• move the fulcrum right

• move the heavier weight back

Multiple Choice

To increase the mechanical advantage of a lever

• make sure the fulcrum is in the middle of the lever

• move the fulcrum closer to the load

• move the fulcrum closer to the effort

• use a bigger fulcrum

Multiple Choice

An example of a lever is

• doorstop

• drill

• staircase

• hammer

Multiple Choice

A lever turns back and forth on a

• effort

• load

• work

• fulcrum

Multiple Choice

What class of lever does scissors fall under

• First class

• Second class

• Third class

Multiple Choice

What class of lever is a shovel

• First class

• Second class

• Third class

Multiple Choice

What class of lever is a wheelbarrow

• First class

• Second class

• Third class

Inclined plane

It is a plane flat sloping surface set at an angle with a horizontal surface.

How does it operate?

• The longer the distance between the object and the surface the less force or effort is applied to raise the object.

• The shorter the distance between the object and the surface the more force or effort is applied to raise the object.

Characteristics of an inclined plane

• It is mainly a ramp

• It is large and flat

• It is tilted so that one side is higher than the other side.

• Everyday examples of inclined planes include highway access ramps, sidewalk ramps, stairs, wheelchair ramps, loading ramps, playground slide, boat ramps, inclined conveyor belts, etc.

Applications of inclined plane

• The sloping surface helps to do work by allowing load to be moved to a lower or higher surface with less effort.

• Inclined planes make it easier to lift something. For example, think of a ramp; engineers use ramps to easily move objects to a greater height. There are two ways to raise an object: by lifting it straight up, or by pushing it diagonally up.

• Lifting an object straight up moves it over the shortest distance, but you must exert a greater force. 

• On the other hand, using an inclined plane requires a smaller force, but you must exert it over a longer distance.

• To make a way for easy access into a building for those on wheelchairs.

Multiple Choice

A ramp is an example of a(n)

• inclined plane

• fulcrum

• force

• lever

Multiple Choice

Which simple machine would most likely increase the distance and reduce the force needed for a rolling cart to be moved up three steps?

• LEVER

• SCREW

• PULLEY

• INCLINED PLANE

Multiple Choice

there is a cow in this meeting named toluwani

• true

• false

Multiple Choice

A playground slide is an example of which simple machine?

• pulley

• wedge

• inclined plane

• screw

Multiple Choice

The man is using which simple machine to enable him to lift this heavy weight?

• pulley

• wedge

• wheel and axle

• lever

Multiple Choice

Q3. This is an example of what simple machine?

• PULLEY

• LEVER

• SCREW

• INCLINED PLANE

Multiple Choice

A flat sloping surface that connects lower and higher elevations. It makes raising objects easier.

• wedge

• SCREW

• LEVER

• INCLINED PLANE

Multiple Choice

A simple machine that consists a rigid bar that pivot about a fixed point

• LEVER

• PULLEY

• SCREW

• WEDGE

Multiple Choice

A device that has two or more simple machines working together

• FULCRUM

• PULLEY

• compound (complex) machine

• MOTOR

Multiple Choice

The fixed point on the lever is called

• LOAD

• RESISTANCE

• BAR

• FULCRUM

Multiple Choice

Which of the following does a simple machine do?

• allows the users to apply less force over a longer distance

• reduce the amount of force needed to do work

• change the direction of the applied force

• all of the above

Multiple Choice

How can you reduce the amount of force required to lift an object using an inclined plane (ramp)?

• increase the length of the ramp

• increase the height of the ramp

• decrease the length of the ramp

Multiple Choice

Hammers can be used to pull nails out of wood. What type of simple machine is a hammer?

• screw

• lever

• pulley

• inclined plane

Multiple Choice

Thomas is using a screwdriver to pry open a paint can, The screwdriver is being used as

• a pulley

• an inclined plane

• a screw

• a lever

Multiple Choice

In a second class lever, the ______ is in the middle.

• effort

• fulcrum

• machine

• load

Multiple Choice

in a third class lever, the ________ is in the middle

• effort

• load

• fulcrum

How does it operate?

• The smaller the inclined angle the more force produced to do work faster than when the inclined angle is big

• When force is applied at the vertical edge, it changes the direction of the force. That is, it changes a downward force to a sideways force.

Characteristics of a Wedge

• It is a portable inclined plane.

• It moves and is used to increase force—either to raise, separate objects or to hold things together. With a wedge, the object or material remains in place while the wedge moves. 

• A wedge can have a single sloping surface- single wedge (like a door stop that holds a door tightly in place), or it can have two sloping surfaces or sides- double wedge (like the wedge that splits a log in two). An axe or knife blade is a wedge, as is a chisel, plough and even a nail. Most wedges have pointy tips to force things apart.

Screw

It is an inclined plane, wrapped around a cylinder to form a thread.

Examples include: the carpenters screw, bolts and nuts, car jack, clamp, jar lid, spinning stool

and spiral staircase etc.

Characteristics of a screw

• It is shaped like a nail with grooves or holes going down it in a curved or spiral pattern.

Parts of the Screw:

• head: it is a specially formed section on one end of the screw that allows it to be turned or driven.

• It is also called the handle or effort. It is the point of rotation or the point at which the effort is applied.

• The head is usually larger than the body of the screw, which keeps the screw from being driven deeper than the length of the screw. Common tools for driving screws include; screwdrivers and wrenches.

Parts of the Screw

• a shank/shaft: it is the cylindrical portion of the screw from the underside of the head to the tip is known as the shank. It may be fully threaded or partially threaded.

• a pitch (h), the distance / space between each thread is called the pitch.

• 
  

How screws operate (principle)

• As the effort (input force) is applied on the screw head, the screw continuously moves into the load through a distance between two consecutive threads (pitch) until it is completely driven into the load.

• When the effort moves a complete circumference of a circle, the load moves a corresponding distance which is the pitch.

• A common mnemonic device for remembering when working with screws or bolts is "lefty-loosen, righty-tighten.

• A screw turns a twisting motion (rotational / input force / effort) into a straight motion (output force).

• The longer the screwdriver the easier it is to operate the screw. As the handle of the effort arm increases, effort applied is reduced and it becomes easier to operate the machine.

Multiple Choice

Which simple machine is found on the head of an ax?

• wedge

• lever

• pulley

• screw

Multiple Choice

A door stop is an example of a

• screw

• wedge

• lever

• inclined plane

Multiple Choice

This is an example of what simple machine?

• wheel and axle

• wedge

• pulley

• screw

Multiple Choice

What type of simple machine is found on the floor of a bathtub?

• screw

• inclined plane

• wedge

• pulley

Multiple Choice

What simple machine can be used to split things apart and also it can hold open a door?

• lever

• pulley

• wedge

• screw

Multiple Choice

An ax head is a simple machine called a wedge. How can you make the cutting edge more efficient?

• make it longer

• make it shorter

• make sharper

• make it more rounded

Multiple Choice

wheelbarrows, fishing rods and baseball bats are all examples of ________________

• inclined planes

• wedges

• compound machines

• levers

Multiple Choice

Which of these is an example of a wedge?

• skateboard

• broom

• stairs

• butter knife

Multiple Choice

What two simple machines make up scissors?

• wheel and axle

• lever and wedge

• wedge and inclined plans

• inclined plane and lever

Multiple Choice

An inclined plane wrapped around a rod forms this simple machine

• lever

• pulley

• screw

• wedge

Multiple Choice

What simple machine is at the bottom of a Lightbulb

• wedge

• pulley

• inclined plane

• screw

Pulley

A pulley is a type of lever that has a wheel (moving part) on an axle (fixed part), with a groove along the edges to support movement of a cable or rope.

Characteristics of Pulley

• It can work on one, two and more wheels.

• The more pulleys, the easier it is to pull or lift an object.

• If the pulley involved is more, there is a greater distance to pull and it is still easier to lift an object. Therefore, the more wheels you have; the more weight you can lift. This accounts for the mechanical advantage of a pulley system.

It has a system of working with both fixed and movable pulleys, thus it is grouped into three major types: Fixed, Movable and Compound pulleys.

Fixed Pulley:

When a pulley is hinged to a fixed support, it is a Fixed Pulley. It does not mean that it cannot move, it is free to rotate around the fixed pivot.

Examples are mounting up a mast on a flagpole, cargo lift system and blinds.

A Movable Pulley:

It is free to move up and down along with the load and can rotate like the fixed pulley. It is supported by two parts of the same rope and has a mechanical advantage of two. Examples are the construction cranes and gym equipment’s.

Compound Pulley:

It is a combination of the fixed and moving pulley. Examples include- Block and tackle system, elevators, theatre pulley system.

How pulley operates (principle)

• When one end of the rope is pulled downwards, the load on the other end of the rope is pulled upwards. Therefore, the direction of the force is changed from downwards to upwards force.

• The theory of operation for a pulley system assumes that the pulleys and lines are weightless, and that there is no energy loss due to friction.

• The more pulleys, the easier it is to pull or lift an object. If the pulley involved is more, there is a greater distance to pull and it is still easier to lift an object. Therefore, the more wheels you have; the more weight you can lift. This accounts for the mechanical advantage of a pulley system.

Application of the pulley system

• A cargo lift system that allows items to be lifted to higher floors.

• Cranes that lift heavy load into a ship or other automobiles.

• Theatre pulleys for the operation of curtains and lowering or raising of pieces of scenery during a theatrical performance.

Multiple Choice

________ reduces the effort needed to raise an object by changing the direction of the force. The force is applied in the downward direction

• Pulley

• Screw

• Wheel and axle

• Wedge

Multiple Choice

Identify the type of pulley

• FIXED PULLEY

• MOVABLE PULLEY

• COMPOUND PULLEY

• NONE OF THE ABOVE

Multiple Choice

IDENTIFY THE TYPE OF PULLEY

• FIXED

• MOVABLE

• COMPOUND

• NONE OF THE ABOVE

Multiple Choice

IDENTIFY THE PULLEY

• FIXED

• MOVABLE

• COMPOUND

• NONE OF THE ABOVE

Multiple Choice

a type of lever that has a wheel (moving part) on an axle (fixed part), with a groove along the edges to support movement of a cable or rope.

• INCLINED PLANE

• PULLEY

• WEDGE

• WHEEL AND AXLE

Multiple Choice

________ is a combination of the fixed and moving pulley.

• FIXED PULLEY

• MOVABLE PULLEY

• COMPOUND PULLEY

• PULLEYCOMPLEX

Multiple Choice

A MOVABLE PULLEY HAS A MECHANICAL ADVANTAGE OF ___-

• 1

• 2

• 3

• 4

WHEEL AND AXLE

It is made up of a large wheel (disc) and a smaller cylinder/wheel/rod (axle) both joined rigidly at the center.

Characteristics

• There may be one or two wheels rigidly joined to the axle.

• The axle allows the wheel to move or move other things.

• It is a type of first-class lever, usually referred as round lever. The fulcrum is where the axle joins the wheel, the effort is the outlying of the wheel and the load is the axle.

• A wheel alone or an axle alone is not a simple machine, they must be rigidly joined to be called a simple machine.

• It has two component parts; a round wheel, and a handle axle for turning the wheel and the load attached to it.

• The first part of a wheel and axle is the large wheel of radius R that may or may not be grooved to take a rope or any other object and the second part the axle of radius r.

• Examples of wheel and axle include ferris, steering wheels, vehicle and cyclist wheels, roller blades, doorknobs, screwdriver and screw, pencil and sharpener.

How a wheel and axle operate (principle)

• For each complete rotation of the large wheel, there is a complete rotation of the axle. Thus, in every complete rotation of either the wheel or axle, the load wind or wound around the axle moves a distance equal to the circumference/rotation of the wheel.

• The rotation of both the wheel and axle causes the applied force to be transferred from one end to the other end.

• The applied force (effort) at the rim of the wheel is increased or amplified at the axle by the rope or string wound round the axle or small wheel to lift or move a larger load.

Application of wheel and axle

• The Wheel and axle are perfect for turning turbines and fans.

• They are also used in automobiles. For example, when you turn the steering wheel of a car, your effort is multiplied by the axle and results in more turns of the car wheels. Also, the wheels of a wagon and bicycle.

• It makes it easier to move an object by reducing the friction involved in moving an object.

Multiple Choice

Identify this simple machine

• lever

• wheel and axle

• inclined plane

• wedge

Multiple Choice

This picture shows an example of what type simple machine?

• pulley

• wedge

• lever

• wheel and axle

Multiple Choice

A doorknob is an example of a

• wheel and axle

• pulley

• inclined plane

• wedge

Multiple Choice

A wheel and axle

• helps move objects when a wheel turns around a rod.

• is made up of two inclined planes.

• is a wheel with a groove for a rope.

• is used to lift heavy objects.

Multiple Choice

Which ramp will require the least amount of force?

• A

• B

• C

• D

Multiple Choice

Josh is pushing wood in a wheelbarrow. What 3 simple machines are in use?

• inclined plane, screw, pulley

• inclined plane, lever, wheel and axle

• inclined plane, screw, wheel and axle,

• inclined plane, wheel and axle, pulley

GEAR

It is a rotating machine made up of toothed wheels (or cylinder) which interlock or mesh with another toothed wheel or wheels to receive and transmit equal and opposite

forces that cause motion.

Characteristics of gear

• It is sometimes referred as a rotating lever.

• It is made up of two main parts; the driving wheel and the driven wheel.

• The driving wheel drives the driven wheel.

• The driving wheel is the effort wheel and the driven wheel is the load wheel.

• When gears touch, its called meshing, The tighter the mesh between two or more toothed wheels the less chance of it slipping.

• It ranges in size and number however what is most important is the number of teeth in a gear.

How a gear operates (principle)

• It transfers force and motion when the teeth of one gear mesh with the teeth of another gear and each gear rotates around a shaft simultaneously.

• Force applied at the cut teeth of the effort wheel drives the load wheel and motion is produced.

• Connected in this way, the two gears turn in different directions, that is: as one gear turns clockwise the other gear turns counterclockwise.

• Increase force and speed is produced when the driving wheel is larger and has more teeth than the driven wheel and decrease force and speed when the driving wheel is smaller

Gear reduction occurs when the drive gear is smaller or has few teeth than the driven gear

Overdrive occurs when the drive gear is larger or has more teeth than the driven gear

APPLICATIONS OF GEARS

• A gear transfers the energy from the engine to the driving wheel of a vehicle in order to make the wheel to rotate, thereby making the vehicle to move.

• When a vehicle is already moving, changing a gear helps to change the fulcrum of the moving vehicle, making it to move faster, more efficiently and powerful in climbing a hill or in making it run normally.

• It makes it easier for automobiles and complex machines to overcome resistance against motion.

• The gear makes a crushing machine more powerful in crushing hard objects.

Multiple Choice

Two or more gears work together. When they turn, the larger wheel makes the smaller wheel turn faster in the opposite direction.

• True

• False

Multiple Choice

Look at the given picture and label the parts as shown

• 1.load 2.effort 3.fulcrum

• 1.fulcrum 2. effort 3. load

• 1.fulcrum 2.load 3.effort

• 1.effort 2. fulcrum 3.load

Multiple Choice

Which is the drive gear

• left

• right

Multiple Choice

_________ occurs when the drive gear is smaller or has few teeth than the driven gear

• Gear reduction

• Overdrive

• Override

• Underdrive