Monday, 11 October 2010

Using Newton's Laws to explain the direction of the net force in Circular Motion

Newton's 1st Law of Motion
A body will continue in its state of rest or uniform motion unless there is an external resultant force acting on it.

Since the body actually turns/rotates/moves in a circle, there is a resultant force acting on it.

Newton's 2nd Law of Motion
The rate of change of momentum of a body is proportional to the resultant force acting on it.

It travels a uniform speed but it's direction is constantly changing. i.e. there is a change in velocity over time and hence a rate of change of momentum, which according to Newton's 2nd Law, implies that a resultant force exists.

Since only a change in direction results from this resultant force, the direction of the force would have to be perpendicular to the direction of motion.

Hence there is a resultant force acting on the object, directed towards the centre of the circular motion.

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