This lecture note will make your life ten-fold easier in the scope of the problems it addresses. Consider it a talisman. I discovered this a couple of weeks ago when I was solving these problems for my own conceptual understanding. So I waited till I can completely enunciate the big picture. When I confirmed that its valid for all the following problems I made this note and sharing with you.
We need to understand first that Force can be categorized into two types. One is called tangential or collinear force. This component of the force is always along the direction of motion and changes speed of an object. It can change direction once the velocity of the object has become zero. Its NOT centripetal force. It can never make an object go in a plane or 3 D trajectory, as the motion is limited to only one dimension. The object can only go back and forth.
Now look at the other component. Its called a radial force. Its always perpendicular to the direction of motion. This force is called centripetal force, always. Note that its different from what we call central forces.
In consequence, both tangential and radial forces can be central.
What happens when some UV falls on biological molecules? (or any kind) some of these molecules like the wooden pole absorb the energy and there still remains energy which they can emit as visible light. So the UV light kicks the molecules and the molecules in turn emit visible light. This implies that the UV wavelength that the molecules absorbed energy at are very small compared to the wavelength at which they emit visible light. This is always the case.
When we say some materials are fluorescent it means they absorbed higher energy and emitted lower energy radiations of colorful light.
But this has a great deal of application apart from its theoretical interest.
Define an Hour Circle.
Its a bit tricky to define some astronomical parameters and not run into innocent looking misrepresentations of facts. One needs to cool his amber more times than there are parameters, then one gets a feel where and how to begin and give a good description.
Hour Circle is a GREAT Circle, on a celestial sphere ** that, at the same time, passes through one of the celestial poles. Hence it passes through both of the celestial poles*.
A great circle is a circle that passes on a sphere, so that its radius (or diameter) equals to the radius (or diameter ) of that sphere.
If the great circle goes through one of the poles (– so both poles as an imminent condition of this definition) its also called a meridian and this circles’s angular reference wrt one of all possible meridians is called a longitude angle, or simply longitude.
To budding astronomers.
A difference between true velocity and proper velocity. Proper velocity (proper motion) is the motion of a star apparent to the center-of-mass of the solar system. That is, how fast any object (a star) is moving wrt the sun’s position. (in terms of its center-of-mass)
So if a star is close to sun, its true velocity might be as much as it is, but proper velocity can be larger. Proper velocities are often larger when stars are closer, an useful fact in Astronomy.
(How proper velocity is eg useful in Astronomy, should be a good essay type question in Indian University exams, in the course of astronomy, but rather its more useful to remove essay type questions from Exams of University and such essay should be written by students as blogs, and the best blogs can be rewarded, Change should be brought to our education system by innovative thinking and not just by lecturing on outdated spiritual discourses)