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Welcome to a world full of machines!
Machines are objects that make it easier for people to do work. Work means that we are exerting force and moving something.
We won't have to use as much force with our simple machines. Let's learn about the six types of simple machines.
The 6 simple machines are: inclined plane, lever, screw, pulley wheel and axle, wedge.
- Inclined plane. (0:38)
An inclined plane is a ramp that assists moving object up and down heights.
It is a plane surface, set at an angle against a horizontal surface. If Max wants to lift and place this box on a ledge, it is a bit difficult. With the help of an inclined plane, Max can now push the same mass up a sloping surface, with much less effort. This is because, the force required to raise an object at a distance is greatly reduced by increasing the distance over which the force must be applied. So the mechanical advantage is the more distance to cover, the less the force you need to move the load to the raised height.
Did you know that a stair is an example of an inclined plane?
- Lever. (1:41)
The lever is one of the most basic forms of a machine. It helps us lift loads with less effort. A lever can be described as a long rigid body with a fulcrum along its length.
- Load: The object you are lifting.
- Fulcrum: Point at which the lever pivots.
- Effort: The force applied to make the object move.
Levers are classified into three categories depending on the relative position of the load, fulcrum and force.
- 1st class: The fulcrum is in between the effort and the load.
- 2nd class: The load is between the fulcrum and the effort.
- 3rd class: The effort is between the fulcrum and the load.
We use levers in so many of our daily activities.
- Screw. (2:42)
A screw is one of the most commonly used machines in the world. It is a machine that converts rotational motion into linear motion.
A screw has a long and thin metal shaft with threads spiralling along its length. It also has a turning head with a groove where a screwdriver can be used to rotate the screw.
The strength of a screw's hold depends on the width of the threads and the distance between them. The closer and wider the threads, the stronger the hold will be. However, more threads requiere more rotations to attach the screw and wider threads require more force in the rotations.
the mechanical advantage of the screw increases whe the angle of the spiral increases.
The screw has become an integral part of the mechanical age. It can be used to drill holes, hold things together and lift heavy objects.
Did you know that a light bulb is an example of a screw?
- Pulley. (3:53)
Sometimes, it is not easy to lift heavy objects with only human force. This problem can be fixed with the help of a simple machine like a pulley.
A basic pulley comprises of a wheel on a fixed axle, with a groove along the edges to guide a rope. When you put two or more pulleys together you have created a great lifting machine. You increase the mechanical advantage and it becomes very easy to lift the same load.
The trade-off is that as you increase the number of pulleys, you require a greater amount of rope to achive the same result. By decreasing the effort neede to lift the load you have to apply the force for a longer period of time.
- Wheel and axle. (4:54)
When we have to move a really heavy object, we have to use a great deal of force to push it. That is because of:
- Friction: Force resisting the motion of the object on the ground.
- Gravitional force: Force that pulls the object to the ground.
The wheel and axle solves this problem.
In this simple machine, a wheel is locked to a central axle and they rotate each other when a force is applied on either one of them.
When we place a heavy object on the axle and push it, the rolling of the wheels reduces the friction making it easier to move.
We see the wheel and axle in many of our daily activities. Such as when we use a car, a shopping trolley or a wheelchair.
Did you know that a door knob is an example of a wheel and axle?
- Wedge. (6:05)
The wedge is the active twin of the inclined plane. But unlike the inclined plane, which is stationary, a wedge does useful work by moving.
A wedge is made up of two inclined planes. These planes meet and form a sharp edge. For a wedge, the effort is applied to the vertical edge of the wedge.
We often see a wedge being used for many things such as:
- To cut portions of an object.
- To lift heavy loads.
- To hold an object in place and avoid it from moving.
The work yielded from the wedge is inversely proportional to the inclined angle. That means, if the inclined angle is small, the wedge yields more work and may do the job faster, than a wedge with a wider angle.
These were the simple machines that make work much easier to do: Inclined plane, lever, screw, pulley, wheel and axle and wedge.
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