Machines and Movement Part 3


Mechanical Advantage

Mechanical advantage is basically the ratio of the load to the effort. It allows the device to perform the task for which it was designed. It relates to use of a small effort to overcome a large load. Example crushing machines; Mechanisms of this type of machine make use of two flat surfaces. An object is placed between those two surfaces, and using simple hydraulic action, the top surface is moved in the direction of the lower surface. As it moves closer, the factor of mechanical advantage makes it possible to compact the volume of the object into a smaller space. Mechanical advantage(MA) = load ÷effort
Mechanical advantage is a ratio, so it does not have a unit. Example; calculate the MA of on machine when an effort of 5N is applied to one end of crowbar to move a piece of wood of weigh 20N.
Energy converted
Energy converted (work)= force × distance moved in the direction of the force. Work is defined as the size of the force being exerted multiplied by the distance moved in the direction of that force. Work= Force (N) × Distance (m) the unit for work is newton metres, just  like moment of force.  But for work done/ energy converted we refer to these units as joules (abbreviation, capital ‘J’).
combustion 1
Maintaining machines
N.B. A machine is never 100% efficient, some of its energy is used to overcome factor such as friction and moving the load. The efficiency of a machine is calculated using the formula; Efficiency= energy actually used to move the load ÷   energy supplied by the effort × 100%. Please also note the velocity ratio(VR). Velocity ratio(VR)=Distance moved by effort ÷   Distance moved by load. The Efficiency of machine can also be calculated using this formula; Efficiency=MA÷VR × 100%
We should maintain machines in order to keep efficiency as high as possible. Thus resulting in the use of less energy.

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