# Physics 3 - Turning Forces - Circular Motion

Revision Cards for Circular Motion, hope this helps :]

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## Circular Motion

For an object moving in a circle at a constant speed, at any instant:

- The objects velocity is directed along a tangent to the circle

- Its velocity changes direction as it moves round

- The change of velocity is towards the centre of the circle

An object therefore accelerates continously towards the centre of the circle.

So the force on the object acts towards the centre of the circle.

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## Circular Motion 2 (Centripital Force)

Any object moving in a circle must be acted on by a resultant force that acts towards the centre of the circle. This is called the Centripital Force, because it always acts towards the centre of the circle.

- The centripital force on a vehicle moving around a roundabout is due to friction between the tyres and the road.

- The centripital force on an aircraft circling around is due to the combined effect of its weight and the lift force on it. The centripital force is the resultant of these 2 forces.

Factors that affect Centripital Force:

- The speed of the moving object. If it moves too fast, it will go off in a straight line. So the Centripital Force needed increases if the speed increases.

- If the circle is too small, the object will again go off in a straight line. So the Centripital Force needed increases if the radius of the circle decreases.

- Also, the greater the mass of the object, the greater the Centripital Force is.

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