Sewn posted this Message: I was recently showing my grandchildren the effect on a compass needle by the magnetic field surrounding a magnet placed in opposition to the earth’s magnetic field – Magnetism 1.01 no? Their mother then asked me how is it that the earth has a magnetic field. I confidently answered that it was due to the central molten iron core of the earth acting as a magnet, and of course as we learned in Magnetism 1.1 68 years ago on of the ways of creating a magnet is a) by striking it several blows with a hammer while holding it in alignment with the earth’s N/S axis or b) heating it. In both cases this allows the atoms to move more freely and align themselves similarly with the axis. But that started me thinking: We know that heating ANYTHING applies energy to the atoms/molecules and this then causes them to display greater and more violent movement within the body of the material. If these molecules are so agitated, how can this identical phenomenon allow the molecule/atoms of the earth’s core to “settle down quietly” into a N/S configuration and remain so
“Sir, What is actually mass? In my child hood I thought that mass is something which is effected on gravitation…….but later I could see that even light attracted by the gravity….Newtons laws of motion mass is something which always opposes the change in inertia…and from Einstein’s view mass is the another form of energy…… And how we can prove 2 body of different mass accelerates differently by applying same force in the absence of friction and gravity?i am very confusing help me sir… Is it my question is blunder??”
Science is continuing to find newer things and explaining things in different manner based on different theories.
Mass, is commonly referred to as the measure of inertia. Inertia can be experienced even at places where the effect of gravity is not experienced.
To the last part of the question,
On the surface of earth all bodies of different mass have the same acceleration due to gravity.
If we consider two bodies of different masses attracting each other, the force experienced by each will be the same, but the acceleration will be different because a = F/m (greater the mass less will be the acceleration)
Akash Malhotra posted
Real world application, COR –> Bounce produced by pitch, for both spinners & seamers; Contact time –> grip provided by pitch, mainly for spinners
Assuming cricket ball (leather ball) to be a sphere and cricket pitch (hardened soil) to be a flat.
1. Would it be appropriate to assume cricket pitch as elastic-plastic flat and cricket ball as elastic-perfectly plastic sphere for modelling purposes?
2. Does there exist any relationship (empirical or physical), relating coefficient of restitution and contact time between a sphere and a flat to their respective material properties and incident velocity.