Forces and Dynamics

Forces

Drawing Free Body Diagrams

• Normal Reaction is to be drawn at the point where the surfaces are in contact.
• Weight is to be drawn downwards from the centre of gravity of the object. (Weight is almost present in all free body diagrams, do not forget to draw it)
• Applied force is to be drawn at the point where the force is applied.
• Frictional force is to be drawn along the two surfaces in contact.

Special Cases of Equilibrium

• For systems where forces are acting at three of more points, the lines of actions of forces have to intersect at a point or are parallel.

Dynamics

Notes when doing questions on dynamics:

• Remember that in dynamics almost all the quantities are vector quantities, meaning they have both magnitude and direction.
• This means that the direction which is v is positive has to be defined clearly
• Angles and direction of the vectors have to be taken into consideration

·         Special Cases for Head-on Perfectly Elastic Collisions