# Physics P3.2

HideShow resource information
• 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
• 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