Mechanisms and motion
10/10/2010 | wayfarer
Nearly every man-made item that exists wherein there is motion, consists of mechanisms. Mechanisms help us to do so many things. Technically, a mechanism is an assembly of mechanical items, designed for a particular purpose. Mechanisms make up a machine. These machines can include anything from door hinges and watches, to bicycles and fighter jets.
The piece below has been adapted from the "connexions" website. Please complete the short acitivities at the back of your notebook. Feel free to discuss the questions here, but do NOT post the answers:
In our everyday life we are surrounded by mechanisms. They help make our life easier in many ways. Most of the mechanisms you use are so familiar that you never think about them. Simple things like door handles, light switches, parts of a bicycle and a car are only a few examples. In the past, in old machines such as steam engines, the mechanisms were easy to see. Today they are hidden behind panels and covers. Mechanisms allow us to do simple things like switching on lights, running a bath and peddling up the hill easily on a bicycle.
Activity 1
1.1 Make a list of items that you think are examples of mechanisms? Sketches and pictures of these items can also be included.
Mechanisms can be used to change the speed, direction or force required to do something. Mechanisms may be able to help you but they cannot do it on their own. They need energy and someone or something to operate them. The energy that is used by a machine is called the input. The result of this energy input is called the output. A mechanism such as a bicycle can be explained with the diagram below.
Mechanisms are concerned with motion. There are four main types of motion. These can be illustrated by means of human body movements.
Types of mechanisms
Mechanisms are used in machinery. There are five types of mechanism:
1. Levers enable forces to be applied at precise points.
2. Pulleys change the direction and speed of a movement, and allow the transmission of power.
3. Gears transmit rotary motion and force.
4. Cams and cranks convert uniform input motion to non-uniform output motion.
5. Screws allow rotary motion to transmit a linear force.
Activity 2
Answer the following questions based on the pictures A – F.
1. Name the mechanism in each of A - F.
2. Suggest a use for mechanism A.
3. In B, Axle 1 rotates at 10 rpm. How fast will axle 2 rotate?
4. To what use may mechanism C be put?
5. In D, if W rotates clockwise, how can you make V rotate anticlockwise?
6. Sketch a toy that could use mechanism F.
Discuss the usefulness of mechanisms and the above activities here