Physics B3- Forces and Waves

Triple Physics.

Unit 1

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  • Created by: Sam
  • Created on: 10-04-10 15:10

Turning Forces and Centre of Mass

A MOMENT is the TURNING EFFECT of a force

1) A LARGER force would mean a LARGER moment

2)A GREATER distance and the same force would create a LARGER moment

3)For a MAXIMUM moment, it needs to be pushed at right angles

3)Pushing at any other angle means a SMALLER moment

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The centre of mass hangs directky below the point of suspension

1) Centre of mass of an object is where ALL of the mass is concentrated

2) A freely suspended object will swing until its centre of mass is DIRECTLY below the POINT OF SUSPENSION

3) Sometimes you can find the centre of mass by using LINES OF SYMETRY

4) The centre of mass does not necessarily have to be in the object; it can suspend itself in mid air.

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Balanced Moments and Stability

1) if anti-clockwise moments are equal to the equal to the clockwise moments, the object won't turn.

Low and Wide objects are most stable...

1) The most stable objects are ones with wides bases and a low centre of mass

2) An object will begin to tip over if its centre of mass moves beyond the edge of its base

3) Again, because of moments if the weight does not act in line with the pivot it'll cause a resultant moment and tip over

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Circular Motion

Circular motion- velocity is constantly changing

1) Velocity is both speed and direction of an object

2) If an object is travelling in a circle then it's constantly changing direction , which means that it's accelarating

3) This means that there is a force acting on it

4) This force acts towards the centre of the circle

5) This force that keeps something moving in a circle is called a centripetal force

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Centripetal force

Centripetal force depends on mass, speed and radius

1) The FASTER an object is moving, the BIGGER the centripetal force has to be

2) The HEAVIER the object the BIGGER the centripetal force

3) You need a LARGER force to keep it moving in a SMALLER Circle (it has more turning to do)

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Gravity and Planetary orbits

Gravity is the centripetal force that keeps planets in orbit

1) Gravity is the force of attraction between masses- the LARGER the mass, the GREATER the force

2) This gravitational force can act as the centripetal force that keeps one object moving in an ORBIT.

3) An orbit is possible when the forward motion of the object is equal to the force pulling it inwards

4) These orbits are elongated circles (ELLIPTICAL) with the Sun at the focus

5) The further away a planet is from the sun, the longer the orbit takes

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Planetary orbits

Gravity decreases the further you get away

1) Very lar

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