The Spinning World

One week into the third semester and many of you were caught panting and some are still wondering what hits you. I can't say for other subjects but Physics has set many of you in motion, circular motion. Well, we still use Newton's Second Law of Motion ie F=ma. Only this time the line of force is taken along the radius of the circle. Some of you still wonder "why delta t must tends to zero". Well, we are looking at the instantaneous tangential speed and instantaneous angular velocity so that we can formulate the equation v=wr. As for the forces, just divide them into the centripetal force needed ( mass x centripetal acceleration) and the physical forces that made up the force needed ( tension, weight, normal reaction, friction ) Find a vector sum of these forces that acts through the centre of the circle. Then equate the resultant force to that cetripetal force needed. They two must be equal, otherwise circular motion is not possible.

Regarding the vertical circular motion, the speed is constant. There is no need to work out the conservation of energy so that "potential energy lost = kinetic energy gain ". You only do the conservataion of these two energies if the particle is doing the loop soley under the influence of the gravity, there is no other means ( sunch as engine ) to get the extra energy. Increase in kinetic energy has to come from potential energy and vice versa.

I repeatedly reminded you in the class that if you are in doubt, don't hesitate to come to see me but you chose to be in the state of perpectual hesistation and torture yourself, I didn't. Or maybe some of yu have forgotten that it is Mr Tan that teaches you Physics and come looking for Mr T! ( They might mistaken that you are looking for Mr Tiger Wood or the Mr T of the TV series The A-Team )

Next on the menu is Simple Harmonic Motion. Mind you, if you don't iron out the circular motion, then the SHM will be anything but SIMPLE and you won't be harmoneous after the lesson.

*** The A-Team will only be known to those of age 30 and above. Your big brothers/sisters or parents should know.