Module 4 Forces in Action

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How are net force, mass and acceleration of an object related?
F=ma. A force of 1N will give a 1kg mass an acceleration of 1ms^-2 in the direction of the force.
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What is the centre of mass of an object?
A point through which any externally applied force produces straight-line motion but no rotation.
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What is the centre of gravity of an object?
An imaginary point where the entire weight of an object appears to act- it coincides with the centre of mass.
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What is the moment of a force?
The turning effect of a force about a point. Moment = fprce x perpendicular distance from the line of action of force
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How would you calculate a moment that has a non-perpendicular force?
Resolve the force F into two perpendicular directions. xFcos(angle)
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What is the principle of moments?
When a body is in equilibrium, the net force acting on it is zero. For a body in equilibrium, the sum of the anticlockwise moments about any point is qual to the sum of the clockwise moments about that same point.
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What is a couple?
A pair of equal but opposite forces acting on an object- they must be parallel and along different lines.
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How do you calculate the torque of a couple?
One of the forces x perpendicular separation between the forces.
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When can a triangle of forces be used?
When an object is in equilibrium, as the resultant of the three forces is 0, so they can be drawn tip to tail.
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How do you calculate density?
mass/volume
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What is pressure and how is calculated?
The normal force exerted per unit cross-sectional area. Force/Area
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Why do gases and liquids exert pressure on surfaces?
Because of the constant bombardment by their molecules.
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How do you calculate the pressure exerted by a vertical column of any liquid?
pressure= height of the column x density of the liquid x acceleration of free fall
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What is the resultant force on an object submerged in water called and how can it be calculated?
Upthrust = cross-section area x height x density x g.
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What is Archimedes' principle?
The upthrust exerted on a body immersed in a fluid, whether fully or partially submerged, is equal to the weight of the fluid that the body displaces. For a floating object, the weight of the fluid displaced is equal to the weight of the object.
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Other cards in this set

Card 2

Front

What is the centre of mass of an object?

Back

A point through which any externally applied force produces straight-line motion but no rotation.

Card 3

Front

What is the centre of gravity of an object?

Back

Preview of the front of card 3

Card 4

Front

What is the moment of a force?

Back

Preview of the front of card 4

Card 5

Front

How would you calculate a moment that has a non-perpendicular force?

Back

Preview of the front of card 5
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