# Physics P3.2

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- Created by: Will Pound
- Created on: 09-03-14 16:12

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- Physics P3.2
- Moments
- The moment of a force is a measure of the turning effect of the force on an object
- M= F x d
- F= force
- M= moment of the force
- d= the perpendicular distance from the line of action of the force to the pivot

- To increase the moment of a force, increase F or increase d

- Centre of mass
- The centre pf mass of an object is that point where its mass can be thought to be concentrated
- When a suspended object is in equilibrium, its centre of mass is directly beneath the point of suspension
- The centre of mass of a symmetrical object is along the axis of symmetry

- Moments in balance
- For an object in equilibrium, the sum of the anticlockwise moments about any point = the sum of the clockwise moments about that point
- To calculate the force needed to stop an object turning we use the equation >>>

- Stability
- The stability of an object is increased by making its base as wide as possible and its centre of mass as low as possible
- An object will tend to topple over if the line of action of its weight is outside its base
- An object topples over if the resultant moment about its point of turning is not zero

- Hydraulics
- P= F/A
- P= pressure
- F= force
- A= cross sectional area at right angles to the direction of the force

- The pressure in a fluid acts equally in all directions
- A hydraulic system uses the pressure in a fluid to exert a force

- P= F/A
- Circular motion
- The velocity of an object moving in a circle at constant speed is continually changing as the object's direction is continually changing
- Centripetal acceleration is the acceleration towards the centre of the circle of an object that is moving round in a circle
- The centripetal force on an object depends on its mass, its speed and the radius of the circle

- The pendulum
- The time period of a simple pendulum depends only on its length
- To measure the time period of a pendulum, we can measure the average time for 20 oscillations and divide the timing by 20
- Friction at the top of a playground swing and air resistance will stop it oscillating if it's not pushed repeatedly

- Moments

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