# Forces

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• Created by: Hemdev
• Created on: 22-01-16 16:12
• Forces
• Work Done
• the amount of energy transformed (changed) when a force moves (in the directions of force)
• Work is only done when there is movement against an opposing force. For e.g. lifting a book off the floor to put on a table, here the movement is from the floor to the table and the opposing force is the weight of the book.
• Work Done= Force x distance moved in the direction of the force
• W=FxD
• Work is done whenever a force moves something
• Changing Shape
• Elastic material stretch when a force is applied but returns to its original shape when the force is removed
• Plastic stretches but it keeps its new shape even when the force is removed
• the extension is proportional to the force and they obey Hooke's law up to this point known as the limit of proportionality
• After the limit it becomes less stiff and the same increase causes a greater stretch and this point, is the force is removed, it won't return to its original shape
• Forces and electricity
• Elastically Deformed
• If an object is stretch and returns to its original length after the forces have been removed
• In-elastically Deformed
• If an object is stretch and does not returns to its original length after the forces have been removed.
• Hooke's law
• The extension of an object is directly proportional to the force that is applied to it provided that the limit of proprtionality is not exceeded
• How much a certain spring extends depends on the force applied and the spring constant
• This is a measure of the stiffness of the spring and it is measured in newtons per metres (N/m)
• The higher the spring constant the stiffer the spring and the less it extends for a given force.
• Hooke found that the force and extension were only directly proportional up to a certain point.
• The limit of proportionality is called the elastic limit. Up to this point the spring is in its elastic region. Elastic means that it will return to its original shape.
• Force= Spring constan x extension
• Moments
• When you apply a force to something, it might turn about a fixed point
• The fixed point is called a pivot
• The turning effect is called a moment
• Moment of force(Newton-metres, Nm)=Force (Newton, N) x Perpendicular distance from line of action of force to pivot (Metres, M)
• Hydraulics
• Hydraulics system is also known as force multiplier
• The piston where the load is applied is sometimes called the effort side
• The piston at the other end is sometimes called the load side. it has the larger area