Forces-draft


 * Physics Topic // " __ Finding out about FORCES __ " //**


 * **PHYSICS is…** ||

__ Physicists __ study different types of energy. They investigate and explain things like movement, heat, nuclear energy, light and electricity. Some engineers use their knowledge of physics to make sure buildings are strong and cars are safe. Physics knowledge is also used in electronics & computer design. ||
 * The study of the behaviour of natural and manufactured things and reasons for their behaviour. Physics is concerned with movement and different forms of energy such as light, heat, electricity and nuclear energy. Branches of physics include acoustics, the study of sound.

// Learning Aims //

// Key Questions //
 * What are simple machines?
 * How does the design of simple machines provide an advantage?
 * How should they be best employed?
 * How do parts of the body work as simple machines?

** Scientific view **

The word machine has origins in both the Greek and Roman languages. The Greek word ‘machos’ means ‘expedient’ or something that ‘makes work easy’. The Romans have a similar understanding of the word ‘machina’ which means ‘trick’ or ‘device’.

The basic purpose for which most simple machines are designed is to reduce the effort (force) required to perform a simple task. To achieve this, the force applied must act over a longer distance or period of time resulting in the same amount of work being performed by a smaller force. Screws, levers and inclined planes are designed to increase the distance over which the reduced force acts so that we can push or pull with less effort. The effect of this design is often referred to as providing a ‘mechanical advantage’.

The term ‘simple machine’ is commonly used by scientists to refer to one of six different types of devices which are often combined to form more complex machines.

** - The lever (e.g. crowbar or claw hammer) **

Consists of a stiff beam that rotates around a fixed pivot point (fulcrum) located somewhere along the beam. Motion at one end of the beam results in motion at the other end in the opposite direction. The location of the fulcrum can magnify (or reduce) the force applied at one end at the expense (or advantage) of the distance over which the other end travels. ** - The wedge (e.g. log splitter or knife) **

Is used to convert a force applied in the direction of the wedge’s movement to a splitting action that acts at right angles to the blade. It is often used to split, cut or raise heavy objects depending on the angle of the sides of the wedge. ** - The wheel and axle (e.g. steering wheel or screwdriver) **

Combines a wheel with a central fixed axle which ensures that both must rotate together. A small force applied at the edge of the wheel is converted by rotation to a more powerful force at the smaller axle. This effect can be reversed by applying a large force to the smaller axle resulting in a smaller force at the edge of the larger wheel with much greater rotational speed. ** - The screw (e.g. scissors style car jack or window winder) **

The rotation of a threaded shaft can be converted into movement in either direction along the axis of rotation depending on the direction of its spiral thread. A screw acts like an ‘incline plane’ that has been wound around a shaft. They are commonly used with gears or as a fastening mechanism. ** - Incline plane (e.g. ramp or staircase) **

Is commonly used to raise or lower heavy objects. The large movement of the object along the ramp is converted by the angle of the ramp’s elevation into a smaller vertical movement. Given the friction on the ramp is small, a reduced force is needed to raise a heavy object vertically although it must be moved a greater distance along the ramp to achieve this advantage. <span style="background-color: #c0ebe0; display: block; font-family: inherit; font-size: 13px; text-align: left; vertical-align: baseline;">** - Pulley (e.g. block or curtain cord) **

<span style="background-color: #c0ebe0; display: block; font-family: inherit; font-size: 13px; text-align: left; vertical-align: baseline;">The use of a single fixed pulley and attached cord allows for a change in the direction of the force applied to an object. Although a single overhead pulley provides no mechanical advantage it may be helpful, for example, in allowing a lifting force to be better achieved by redirecting the force down towards the ground to raise an object. Pulleys can be used in complex combinations to provide large mechanical advantages such as with the design of a ‘block and tackle’.

**ACTIVITIES**

-Simple Machines...
 * What are some machines that you know of?
 * Simple machines are levers, inclined plane, wedges and pulleys.

// Resources //