Homework

Due Friday homework was set upto Q20 Page 190

Homework now complete to Q25

In Class we cover Q 20 and how the area under a VT curve is the displacement , the gradient is the acceleration.

We are now in a position to Revise Newtons 3 Laws:

N1: With no forces, their velocity is unchanged.

This is historical reference to the different ideas of Aristotle of Violent, and curved motion.

N2: Sum of forces = product of acceleration and mass

Here the idea of forces need to be developed. Internal forces are found the product of an external field and an objects field force factor. For gravity the field is described by g and the number inserted to create the force is the Mass. In this case we draw the force on the object, determined by the field direction and the size by the size of the field and multiplier factor. The are also external forces mostly generated by strings or by contact with surfaces. Here we draw pairs of forces at the point of contact.

The sum of forces = a resultant force, ie a single force that does not add up. and this is the acceleration.

N3 F12=-F21 for every force there is an equal and opposite force. In the case of internal forces where the force vector is inserted, there is an opposite force but it is just not on the diagram. For contact forces we draw a pair of forces that cancel. This law basically leads to the concepts of momentum transfere, and the conservation of momentum as the forces balance.