Physics lesson: Simple Machines. Article contents and topics:
Machines made of very few parts, which only use a single type of force, are called simple machines. Simple machines can be found in many places in everyday life.
In the picture above, force can be applied to the prybar in the directions shown by the numbered arrows. In which direction should force be applied to pull the nail out of the board more easily?
In everyday life, we use many tools built by taking advantage of changing the direction of a force. These tools make it easier for us to do work.
The purpose of simple machines is to make doing work easier by changing the magnitude and direction of the applied force.
Properties of Simple Machines
- They make work easier. However, there is no gain or loss in the work itself. As a result of the work, they don’t produce any gain or loss in energy either. They also don’t save energy.
- Simple machines allow the direction, magnitude, and point of application of a force to be changed.
- There is a gain in either force or distance. However, both gains cannot be achieved at the same time.
- Energy must always be used when work is done with a simple machine.
A gain in force in a simple machine happens because the input force is smaller than the output force. In other words, tasks that require a large force can be done with a small force.
Lever Principle
Levers change the effort arm relative to the fulcrum, allowing heavy loads to be moved with little force.
Inclined Plane Advantage
An inclined plane lets you move a load along a longer path that requires less force, instead of lifting it directly.
Pulley Systems
When fixed and movable pulleys are used together, the pulling force needed can be reduced depending on the number of pulleys.
What Are Simple Machines?
Levers
A lever is a device consisting of a sturdy rod that can rotate about a fulcrum point.
In a lever, the distance from the force to the fulcrum is called the effort arm, and the distance from the load to the fulcrum is called the load arm.
In levers
the relationship: force x effort arm = load x load arm applies.
The longer the effort arm is compared to the load arm, the greater the mechanical advantage in force.
The farther the applied force is from the fulcrum, the smaller it needs to be; if the load is close to the fulcrum, less force needs to be applied; if the applied force is close to the fulcrum, it needs to be greater.
In the figure alongside, the worker applies the greatest force in position 1, and the least force in position 3.
Types of Levers and Everyday Examples
We can say there are different types of levers depending on the position of the fulcrum and the applied force. Simple machines have more uses in our lives than you might think.
TYPE 1: Simple machines that work on the lever principle with the fulcrum in the middle include examples such as pliers, scissors, seesaws, tongs, crowbars, and equal-arm balance scales.
TYPE 2: The fulcrum is at one end, the force at the other. Simple machines that work on this lever principle include examples such as a nutcracker, a wheelbarrow, and a bottle opener.
TYPE 3: The applied force is between the fulcrum and the load. For example: a tennis racket, tweezers, an oar, tongs, a forearm muscle, a hockey stick, etc.
The saying of Archimedes, the inventor of the lever, about the lever expresses to us the magnitude of the mechanical advantage a lever can provide.
Pulleys
Pulleys are among the devices we can call simple machines. They are simple machines that can rotate freely around a fixed axle and have a groove around their circumference for a rope to pass through.
Fixed Pulleys
A pulley hung from a fixed point that rotates to make it easier to move objects is called a fixed pulley.
The object can only be lifted with a force equal to its own weight. There is no gain in force.
It only makes work easier by changing the direction and line of action of the force.
Movable Pulleys
These are pulleys that move together with the load attached to the pulley’s axis of rotation.
These pulleys provide a gain in force. For example, in the pulley system shown in the figure, if the load is 100 kg, we can lift the load with a force of 50 kg.
Block and Tackle
This is a system of pulleys made up of fixed and movable pulleys, intended to provide a gain in force.
This gain depends on the number of rope strands passing through the movable pulleys that make up the block and tackle. In the figure, the system on the left has a force gain of 1/2, while the system on the right has a force gain of 1/4.
Inclined Plane
These are simple machines that provide a gain in force by lengthening the distance traveled.
On an inclined plane, the force travels a distance equal to the length of the incline, while the load travels a distance equal to the height of the incline.
F . d = G . h
A screw is an inclined plane wrapped around a cylindrical rod. A screw is one of the most commonly used simple machines for joining two surfaces together. To drive a screw into wood, force must be applied by turning it with a screwdriver.
Gears
Gears are cylindrical-shaped simple machines with teeth spaced evenly around them, able to rotate about an axis. The teeth allow the gear wheels to mesh with one another. A force applied to one gear is transmitted to the other by way of the teeth.
For meshing gears, each gear relative to the one before it,
a. Rotates in the opposite direction.
b. Has a rotational speed inversely proportional to its radius.
Concentric gears, since they are riveted to one another, always rotate in the same direction and have the same rotational speed.
Where n is rotational speed, nK = nL
See related topic: Types of Gears
Pulleys (Belt Pulleys)
Since pulleys have no teeth, they are connected to each other by a belt or a rope. They are generally used to transmit motion taken from a motor to another point. Their rotational speeds are also inversely proportional to their radii. Their direction of rotation, however, changes depending on how the belts are connected, as shown in the figure. In the picture on the left, both pulleys rotate in the same direction, while in the other picture, the two pulleys rotate in opposite directions to each other.
Related Questions
No, simple machines don’t provide any energy gain; they only make work easier to do by changing the direction or magnitude of the applied force. The total amount of work done actually stays the same.
Since energy stays constant, when work needs to be done with less force, the distance over which that force is applied must increase. In other words, a gain in force is balanced by a loss in distance; the two cannot be gained at the same time.
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