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Forces revision - Coggle Diagram
Forces revision
Moments
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The force on a spanner causes a turning effect of moment on the nut (which acts as a pivot). A larger force or a longer distance (spanner) would mean a larger moment.
To get the maximum moment you need to push at a right angle to the spanner. Pushing at any other angle means a smaller distance so a smaller moment
If the total anticlockwise moment equals the total clockwise moment about a pivot, the object is balanced and won't turn.
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Levers increase the distance from the pivot meaning that less force is needed to get the same moment.
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Different sized gears can be used to change the moment of the force. A force transmitted to a larger gear will cause a bigger moment, as the distance to the pivot is greater
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Pressure and depth
As depth of a liquid increases, the number of particles above that point increase. The weight of these particles adds to the pressure felt at that point, so liquid pressure increases with depth
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As these particles move, they collide with others
Particles are light but they still have a mass and exert a force on the object they collide with. pressure is force per unit area, so the particles exert a pressure
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Pressure (pa) = height of the column of liquid (m) x density (Kg/m^3) x gravitational field strength (N/Kg)
Atmospheric pressure
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As altitude increases, pressure decreases as the atmosphere gets less dense so there are less molecules to collide
There are also fewer air molecules above a surface as the height increases so the weight of the air above it decreases with altitude
Upthrust
When an object is submerged in a fluid, the pressure of the fluid exerts a force on it from every direction
Pressure increases with depth, so the force exerted on the bottom of the object is larger than the force acting on the top of the object
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If the upthrust on an object is equal to the object's weight, then the forces balance and the object floats
If an object's weight is more than the upthrust, the object sinks
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Springs
When you apply a force to an object you may cause it to stretch, compress or bend
To do this, you need more than one force acting on the object - otherwise the object would just move in the direction of the applied force
Work is done when a force stretches or compresses an object and causes energy to be transferred to the elastic potential energy store
It is is elastically deformed, all this energy is transferred to the objects elastic potential energy store
If an object has been elastically deformed, it can return to its original length and shape after the force has been removed
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An object has been inelastically deformed if it doesn't return to its original shape and length after the force has been removed
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Resultant forces
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Balancing foces
An object is in equilibrium if the forces are balanced (if all of the forces acting on it combine to give zero)
Elasticity
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There is a limit to the amount of force you can apply to an object for the extension to increase proportionally, this can be represented by a graph
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Work done
When a force moves an object through a distance, energy is transferred and work is done on an object
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One joule of work is done when a force of one newton causes an object to move a distance of 1 metre.
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terminal velocity
When falling objects first set off, the force of gravity is much more than the frictional force slowing them down, so they accelerate
As the speed increases, the friction builds up
This gradually reduces the acceleration until eventually the frictional force is equal to the accelerating force
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Newton's laws
Newton's first law
If the resultant force on a stationary object is zero, the object will remain stationary. If the resultant force on a moving object is zero, it will continue moving at the same speed in the same direction
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