Неплохой topic simple machines. Методическая разработка занятия по английскому языку на тему "Машины и работа" (3 курс)

• Distribute small toy cars that have wheels joined by axles to groups of students. Kick-start a discussion with some questions about the toy car mechanics, such as: How do these toy cars move? How are the wheels on each side of the car joined to each other?
• Have a student volunteer point to the rod that holds the two wheels together. Explain that the bar that joins two wheels is called an axle .
• Tell students that they will be learning about wheels and axles.
• Hold up the doorknob, explaining that it is an everyday example of a wheel and axle.
• Challenge the students to help you identify the wheel and axle in the doorknob. Listen as different students call out their guesses.
• After some speculation, tell students that the knob that turns is the wheel. The inner rod that is attached to the knob is the axle.
• Demonstrate how the wheel and axle works by turning the knob (wheel). That turns the inner rod (axle) and moves the latch, to open the door.

Guided Practice

• To consolidate student thinking, set up activity stations with play dough and a rolling pin.
• Let students practice flattening the dough with the pin.
• Guide them to express these understandings: The rolling pin is a wheel and axle. When you push on the handles (the axle) the wheel turns and flattens out the dough.
• Challenge students to think of other common machines that have one wheel like the rolling pin. Great examples include a wheelbarrow, a top, and a playground merry-go-round.

Independent working time

• Pass out a copy of the Wheel and Axle worksheet to each student to complete independently.
• Walk around the classroom to offer support to students who get stuck.

Differentiation

• Enrichment: Have students who need more of a challenge read a history of other simple machines, and fill out an accompanying word search.
• Support: Put students who need more support into pairs to complete the Wheel and Axle worksheet.

Assessment

• Collect the work sheets that the students have filled out, and correct them using the Wheel and Axle answer sheet.

Review and closing

• In summary, remind students that the rolling pin is a wheel and axle. When you push on the handles (the axle) the wheel turns and flattens out the dough.
• Challenge students to think of other common machines that have one wheel like the rolling pin, such as a wheelbarrow, top, and merry-go-round.
• Remind your class that the wheel and axle is only one of six common simple machines that help things move. For homework or additional independent work, consider encouraging students to learn more about other kinds of simple machines.

Simple machines are tools that make work easier. They have few or no moving parts.These machines use energy to work. There are six types of simple machines . The six types of simple machines are used in our daily life. Simple machines convert a smaller amount of force exerted over a larger distance to a greater amount of force exerted over a shorter distance, or vice versa. The concept of simple machine was introduced by the Greek philosopher Archimedes the 3rd century.

There are six types of simple machines. The six types of simple machines are

• Wedge
• Lever.

Pulley is wheels and axles with a groove around the outside

A pulley needs a rope, chain or belt around the groove to make it do work

Examples: Flag post, Elevator, Window blinds, Crane, Winch.

A screw is an inclined plane wrapped around a shaft or cylinder.

The inclined plane allows the screw to move itself when rotated

Examples: Screw lid jar, drills, door lock, meat grinder, brace and bits,

3) Wedge:

A wedge is used to split an object through the application of force. It is made up of two inclined planes which meet to form a sharp edge. Wedges are used to split things.

Examples: Knives, axe. Forks, pin, chisels.

An inclined plane is a flat surface that is higher on one end, which makes it easier to move heavy objects to a certain height.

Examples: Roller coaster, stirs, sloping roads, ramps, boat propeller,

The wheel and axle is made up of two circular objects. The wheel is the larger object which turns around the smaller object the axle. The axle is a rod that goes through the wheel which allows the wheel to turn,

Examples: Door knobs, Egg beater, Steering wheels, door knobs, pencil sharpener. Gears are a form of wheels and axles

6) Lever:

This is a is a bar rests on a turning point. The turning point is the fulcrum. An object the lever moves is the load. There are three kinds of levers, First order, Second order and third order.

In a first class lever the fulcrum is in the middle and the load and effort is on either side.

Example: see saw

In a second class lever the fulcrum is at the end, with the load in the Middle.

Example: wheelbarrow

In a third class lever the fulcrum is again at the end, but the effort is in the middle.

Example: Pair of tweezers.

Advantage of using the six simple machines:
These six simple machines are used in day to day life. They make the work easier for us. Simple machines are being used hundreds of years before. Even the great pyramids were build by using the simple machines. The inclined plane was used to move heavy stones for building the pyramids. Different combinations of these six simple machines can be used in the building of complex machines.

Sub Topics

The effort is the force applied to the machine.

The load is the force against which the machine does the work.

This ratio is a measure of the advantage that one obtains by using the machine. If a load of 40 N is moved by applying an effort of 10 N on the machine then the mechanical advantage of the machine is given by

Velocity Ratio (V.R)

The "corresponding distance" is the distance moved by the load in the same time as the distance moved by the effort.

The velocity ratio depends only on the design of the machine and is always same for a particular machine. The mechanical advantage on the other hand can vary for a particular machine as it depends on friction.

M.A., V.R. and efficiency have no units as they are ratios between similar quantities.

Effort: The force applied to the machine.

Load: The force against which the machine does the work.

Since the effort does the work on the machine and the load is worked upon by the machine, efficiency can also be expressed as

The efficiency is very often expressed as a percentage i.e.,

It should be noted that 100% efficiency is possible only for an ideal (imaginary) machine. Usually, for all practical purposes the efficiency of a machine is always less than 100%. This is because practical M.A. is always less than theoretical M.A. due to friction and the weight of the moving parts.

How Simple Machines Work

What is a simple machine and how do they work? I"m so glad you asked! Machines make work easier by changing the size of force, direction of force, or distance the force acts on.

Lifting a car with a flat tire and loosening the lugnuts can be accomplished by a single person thanks to simple machines. The jack and lug wrench are simple machines that alter the force needed to change the tire.

Six Simple Machines

Simple machines are basic devices used to alter the force needed to accomplish a task. There are six types of simple machines.

• lever
• wheel and axle
• inclined plane
• wedge
• screw
• pulley

The first type of simple machine is the lever. A lever is a rigid bar that rotates on the fixed point of a fulcrum and changes the distance or size of a force.

There are three classes of levers. A first class lever has an input force and output force on either side of the fulcrum. This causes the output to move in the opposite direction of the the input force. An example of a first class lever is a see-saw. A second class lever has an output force between the input force and fulcrum. This changes the distance of the force. A wheelbarrow is a second class lever. The third class lever has the input force between the output and fulcrum. A broom is a third class lever.

Wheel and Axle

The wheel and axle make work easier by changing the distance the force acts on. A wheel and axle consists of two disks or

cylinders with different radiuses. Examples are a steering wheel and shaft, a car wheel and axle, and a screwdriver.

Inclined Plane

An inclined plane is a slanted surface on which a force can move an object to a different elevation. Why do gentler slopes and ramps require less energy to move a load on? Because the input force required to travel the greater distance of a slope is changed to the smaller distance of the output force – the upward motion.

A wedge is a device made of two back to back inclined planes and is used to split objects. When a wedge is driven into a log, the size of the input force at the wider top of the wedge is changed to greater output force at the narrower point forcing the wedge through the wood. Knife blades are an example of a wedge.

A screw is an inclined plane wrapped around a cylinder. Screws with threads closer together require

less force to turn because the length of the inclined plane is longer. Nuts and bolts are screws. A nut is a screw with the threads on the inside.

The last type of simple machine is the pulley. A pulley consists of a rope that fits into a groove in a wheel. A pulley makes work easier by changing the direction or direction and size of the force.

There are three types of pulleys . They are the fixed pulley, moveable pulley and pulley system.

The fixed pulley is a single fixed pulley and rope. This changes the output direction of the force, making it opposite of the input. When you pull down on a fixed pulley a weight is lifted up.

A moveable pulley is fixed to the object being moved instead of a fixed location. Moveable pulleys multiply the input force needed to lift a heavy object thus reducing the force needed to lift heavy objects. Moveable pulleys are used to move ship sails and window washer platforms.

Pulley systems combine fixed and moveable pulleys to create large mechanical advantages. A crane uses pulley systems to lift enormous loads like locomotives.

References

• Michael Wysession, David Frank, Sophia Yancopoulos. Physical Science Concepts in Action. p.417 – 435. New Jersey: Prentice Hall, 2004.

12 3.0 8.3 25 75 10

29 1.7 3.5 28 350 10

Participant Scores 12 Jacob Joey Daniel David Nicole B.

A single pulley is used to hoist a safe with a mass of 45. 0 kg
A single pulley is used to hoist a safe with a mass of 45.0 kg. If the machine is 100% efficient, what effort force will be required to hoist the safe? 45.0 N 90.0 N 205 N 266 N 441 N 10

A snow shovel is an example of which type of lever? (Hint: The handle of the shovel is the fulcrum.) 1st Class 2nd Class 3rd Class 10

How long must an inclined plane be to push a 100 kg object to a height of 2.0 meters using a force of 200 N? Friction can be ignored. 2.0 m 9.8 m 50 m 100 m 200 m 400 m 10

A wheel and axle machine requires an effort force of 5.0 N to lift a load with a mass of 5.1 kg. If the machine is ideal and has a wheel radius of 12 cm, what is the radius of the axle? 1.0 cm 1.2 cm 5.0 cm 10 cm 1.2 m 2.4 m 10

Participant Scores 28 Jacob Joey Daniel David Mackenzie

20 N 25 N 196 N 245 N 1960 N Answer Now 10

What force will be required to push a 500 N box to a height of 2.50 meters on a ramp that is 10.0 meters long and 85% efficient? 4.00 N 50.0 N 106 125 N 147 N 10

1 2 3 4 5 10

0.50 1.00 1.50 2.00 2.50 Answer Now 10

Participant Scores 44 Jacob Mackenzie 39 Nicole F. Joey Daniel

A ramp is 12 meters long and 3.0 meters high. It takes 145 N of force to push a 400 N crate up the ramp. Determine the efficiency of the ramp. .36 % .69 % 3.0 % 8.2 % 36 % 69 % 145 % 10

An object is placed 1. 75 meters from the fulcrum of a lever
An object is placed 1.75 meters from the fulcrum of a lever. The effort force is 0.50 meters from the fulcrum. What is the actual mechanical advantage if the lever is 95% efficient? .271 .286 .301 3.33 3.50 3.68 Answer Now 10

20% 31% 69% 80% 87% 96% Answer Now 10

Participant Scores 56 Jacob Mackenzie 51 Nicole F. Joey Daniel

A certain ramp is 10 meters long and is 50% efficient
A certain ramp is 10 meters long and is 50% efficient. It requires 25 N of force to push a 50 N crate up the ramp. How tall is the ramp? 1.0 m 2.0 m 2.5 m 3.5 m 4.0 m 5.0 m 22
Participant 1 Participant 2 Participant 3 Participant 4 Participant 5 Participant 6 Participant 7 Participant 8 Participant 9 Participant 10

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Simple machines are extremely important to everyday life. They make stuff that is normally difficult a piece of cake. There are several types of simple machines. The first simple machine is a lever. A lever consists of a fulcrum, load, and effort force. A fulcrum is the support. The placing of the fulcrum changes the amount of force and distance it will take in order to move an object. The load is the applied force. The effort force is the force applied on the opposite side of the load. Levers can be placed in three classes. The 1st class levers are objects like pliers where the fulcrum is at the center of the lever. The 2nd class of levers are objects that have the fulcrum on the opposite side of the applied force like a nutcracker. The 3rd and final class is objects like crab claws. These objects of the load at one end and the fulcrum on the other.

An inclined plane is another simple machine. Inclined planes are also known as ramps. Ramps make a trade off between distance and force. No matter how steep the ramp, the work is still the same. A winding road on a mountain side is a good example of a ramp. Some simple machines are modified inclined planes. The wedge is one of those machines. One or two inclined planes make up a wedge. Saws, knives,needles, and axes are made from wedges. The screw is another modified inclined plane. Screws decrease the force but increase the distance. The ridges are called threads. A couple of simple machines are made with wheels. The wheel and axle is one of these machines.

These are made with a rod joined to the center of a wheel. They can either increase distance or force, depending on the size of the wheel. The pulley is another machine that uses wheels. The are a wheel with a groove in the center with a rope or chain stretched around it. The load attaches to one end and the effort is applied to the other on all pulleys. There are two types of pulleys. The fixed pulley stays in one place while the wheel spins. Movable pulleys attach to objects. Several pulleys can be used at one time. A good example of a pulley system is an escalator. Simple machines make up compound machines. We use these machines daily. Life would be difficult without simple machines.

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