# GCSE Physics P3 [Part 2]

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TURNING FORCES AND THE CENTRE OF MASS:

• Moment= force x perpendicular DISTANCE from the line of action of the force to the pivot

• To get the maximum monent of turning effect you need to push at right angles (perpendicular) to the pivot

• The centre of mass hangs directly below the point of suspension. You can think of the centre of mass of an object as the point at which the whole mass is concentrated.

BALANCED MOMENTS AND LEVERS:

• Total anticlockwise moments = Total clockwise moments

• Examples of simple levers as force multipliers; Long sticks or bars, wheelbarrows, scissors

• Levers make it easier to do work by moving the distance the force is applied further from the period

MOMENTS, STABILITY AND PENDULUMS:

• If the total anticlockwise moments do not equal the total clockwise moments, there will be a Resultant moment, so the object will turn.

• Low and wide objects are more stable.

• The time taken for the pendulum to swing from one side to another is called the 'time period'.

The time period for each swing of a given pendulum is always the same- This is what makes pendulums perfect for keeping time in clocks.

• Time period= 1 / Frequency

• The longer the length of the pendulum, the greater the time period. So, the shorter the length, the shorter the time period. Some examples of pendulums are playground swings, old-style clocks and those wreck-ball thingys.

HYDRAULICS:

• Liquids are virtually incompessible- You can't squash them, their volume and density stay the same. Because liquids are incompressible and can flow, a force applied to one point in the liquid will be transmitted (passed) to other other points in the liquid.

• Imagine a balloon full of water with a few holes in it. If you squeeze the top of balloon, the water will squirt out of the holes. This shows that force applied to the water at the top of the balloon is transmitted to the water in other parts of the