SIMPLE MACHINESSPH4C

Findlay

The student will learn about the main purposes and the basic components of all machines.

What do you think of when you hear the word “machine”?

Simple Machines

Machines created thousands of years ago and even the machines used today are still based on basic machines. Tools such as arrows (wedges) and ramps (inclined plane) are examples of simple machines.

Simple Machines

A Machine is a device that helps perform tasks. It is designed to achieve at least 1 of the 5 main functions.

The Purposes of Machines

Change energy from one form into another. Example: hydroelectric – converts the

energy of falling water into electrical

The Purposes of Machines

Transfer forces from one object to another. Car transmission – transfers the force from the

motor to the wheels

The Purposes of Machines

To reduce the amount of force that is required for a job.

The Purposes of Machines

To modify the speed of something.

The Purposes of Machines

To change the direction of motion. Flag pole – pull down on the rope to raise

the flag by a pulley system.

The Purposes of Machines

It is usually a trade-off between force and speed

For Example… A block and tackle makes it easier to lift

a heavy object but it rises more slowly

The Purposes of Machines

A ramp makes it easier to lift something but you have to move it farther to get it to the same height.

The Components of Machines Complex Machines are known as

compound machines Compound machines are made of…

Simple Machines: Lever Family A lever is a rigid bar that can rotate

freely around a support called a fulcrum.

Simple Machines: Lever Family Levers are divided into three classes,

depending on the position of the load, effort force, and the fulcrum.

Simple Machines: Lever Family

Simple Machines: Lever Family An effort force, FE, is a force applied to one part of

a lever to move a load at another part; the load exerts a load force, FL.

The perpendicular distance from the fulcrum to the effort force represents the effort arm, symbol dE, and the perpendicular distance from the fulcrum to the load force represents the load arm, symbol dL.

dL

Simple Machines: Lever Family The Wheel and Axel

Apply force to the wheel (makes it

easier)Apply force to the axel

(makes it go faster)

Simple Machines: Lever Family The Pulley

This one changes the direction of the force

Simple Machines: Lever Family Gears

These also change the direction of

motion

Simple Machines: Inclined Plane Family

Basic Inclined Plane - A ramp that increases the load that can be raised by an effort force.

Simple Machines: Inclined Plane Family

Screw – an inclined plane wrapped around a central shaft..

Seven Archimedes screws pump wastewater in a treatment plant in Memphis, Tennessee, USA. Each of these screws is 96 inches (2.44 meters) in diameter and can lift 19,900 gallons per minute

Simple Machines: Inclined Plane Family

Wedge – Two inclined planes back to back that increases the applied or effort force.

What is the Simple Machine?

Lever

fulcrum

What is the Simple Machine?

Inclined Plane

What is the Simple Machine?

Screw

What is the Simple Machine?

Pulley

What is the Simple Machine?

Lever - handles

Wedge- blades

What is the Simple Machine?

Lever (handles)

Wedge (blades)Gears

TORQUESPH4C

Findlay

The student will be able to solve problems involving torque, force, load-arm length, and effort-arm length as they relate to levers.

Feeling Torque

When a force or set of forces causes a rigid body to rotate, we say a torque has been applied.

Torque – the turning effect caused by a force on a rigid object around a axis or fulcrum, symbol T; it is measured in Newton-meters, or Nm; it can be called a “moment force”.

Torque on Doors

Every time you open a door, you are producing a torque on the door.

A small force applied far from the hinges can produce the same amount of torque as a large force applied closer to the hinges.

Distance

Distance

Torque

In order to create the largest amount of torque possible when pushing on the door, the force generated must be at a 90 degree angle to the door.

Magnitude of Torque

The amount of torque produced depends on two factors.

1. The magnitude of the force (F) applied to the rigid object.

2. The distance (d) between the force and the axis or fulcrum.

Amount of Torque

Using the symbol T for the magnitude of torque, the following statements hold true:

T increases as F increases ( T F) T increases as d increases ( T d)

Torque = force x distance or T = Fd (where F is perpendicular to the ridge object)

Example Problem

Calculate the torque of a wrench experiencing a force of 84 N, a distance of 0.35 m away from the bolt.

𝐹=84 N∴ the  magnitude  of   the   torque  on   the   wrench   is  29 Nm .

Torque on Levers

Two torques can be calculated for a lever: the effort torque (TE) and the load torque (TL).

The associated distances are the effort distance, or effort arm (dE), and the load distance, or load arm (dL).

dEdL

TL

TE

Torque on Levers

Effort torque = effort force x effort armTE = FEdE

Or

Load Torque = load force x load arm TL = FLdL

In each case, the force is perpendicular to the lever, which allows us to deal with magnitudes only, thus avoiding vector signs.

Example Problem

A camper is using a large plank as a first class lever to move a rock. The effort force has a magnitude of 4.5 x 102 N, and the distance from the fulcrum to the effort force is 2.2 m. What is the magnitude of the effort torque produced? (ignore the mass of the plank)

𝐹𝐸=4.5×102N

∴ the  magnitude  of   the   effort   torque  produced   is   9.9×102Nm .

Static Equilibrium of Levers

The word static means at rest. A rigid object that is in static equilibrium is at rest in two ways.

1. It is not moving in any direction2. It is not rotating

Law of the Lever

When a lever is in static equilibrium, the magnitude of the effort torque equals the magnitude of the load torque.

Law of the Lever

This law can be written in the equation form

Effort torque = load torque

Effort force x effort arm = load force x load arm

FEdE = FLdL

For this equation, only the magnitudes of the quantities are considered. This eliminates the need for positive or negative signs.

Example Problem

A camper wants to mount a trailer on blocks for the winter. One corner of the trailer is lifted by applying an effort force using a 3.00 m steel bar. The trailer is applying a load force of 1.8 x 103 N, a distance of 0.45 m away from the fulcrum. Determine the magnitude of the effort force required (ignore the mass of the bar)

Example Problem

𝐹 𝐿=1.8×103N 𝐹𝐸𝑑𝐸=𝐹 𝐿𝑑𝐿

Law of the Lever

For any rigid object, the law of the lever can be stated in more general terms based on which way it is turned.

The clockwise torque is balanced by the counter clockwise torque.

TCW = TCCW

Where TCW = magnitude of the clockwise torque on an object around the fulcrum.

Where TCCW = magnitude of the counter clockwise torque on an object around the fulcrum.