# P3.2 Using physics to make things work

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• Created by: Emily_O
• Created on: 02-02-14 12:08
What is the centre of mass of an object?
The point at where its mass may be thought to be concentrated
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Where is the centre of mass if an object is freely suspended?
Directly below the point of suspension
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Where is the centre of mass of a symmetrical object?
Along the axis/line of symmetry
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Equation for the time for pendulums
T = 1/f (T=time period, s; f=frequency, Hz)
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How does the length of a pendulum affect the time period?
The longer the pendulum, the longer the time period
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What is a moment?
The turning affect of a force
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Equation to caculate size of moment
M=Fxd (M=moment of force,Nm; F=force,N; d=perpendicular distance from the line of action of the force to the pivot,m)
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What should the moments be like if an object isn't turning?
The total clockwise moment must be exactly balanced by the total anticlockwise moment about any pivot
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Equation for calculating the size of the force, or its distance from the pivot, acting on an object that's balanced
W1d1=W2d2
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What happens to an object if the resultant moment about its point of turning isn't zero?
It topples over
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How can you increase the stability of an object?
Make its base as wide as possible and its centre of mass as low as possible
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What is pressure?
Force divided by the area which the force acts on (P=F/A)
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What is the unit for pressure?
The pascal (Pa) which is equal to 1N/m/\2
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What do hydraulic systems do?
Use the pressure in a fluid to exert a force
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What does the force exerted by a hydraulic system depend on?
The force exerted by the system; the area of the cylinder which this force acts on; and the area of the cylinder that exerts the force
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What happens when an object moves in a circle? (circular motion)
It continuously accelerates towards the centre of the circle but this acceleration changes the direction of motion of the body, not its speed
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What is centripetal force?
The force causing the acceleration towards the centre of a circle of an object moving round the circle
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What causes the centripetal force on an object to increase? (3)
If the mass of the object increases; the speed of the object increases; or the radius of the circle decreases
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## Other cards in this set

### Card 2

#### Front

Where is the centre of mass if an object is freely suspended?

#### Back

Directly below the point of suspension

### Card 3

#### Front

Where is the centre of mass of a symmetrical object?

### Card 4

#### Front

Equation for the time for pendulums

### Card 5

#### Front

How does the length of a pendulum affect the time period?