Mr Lim asked us this question: Where is the center of gravity in a pendulum? Here's my answer: the center of gravity is located in the core of the pendulum. it's something like the earth, you have the core,mantle and the crust.the pendulum is like a small earth and the center of gravity works on earth too, so you don't fall off the earth, which is good.

This diagram shows where the center of gravity is:




this is just a small animation about 1 perioid of the pendulum:



Watch more cool animation and creative cartoons at aniBoom

Regarding the previous post, here's some videos you may want to watch (PS: obviously, i don't need to tell you where the source is from. if you really don't know then it's from youtube. :)

This is a rather interesting explnantion about center of gravity as its half-science lesson, half drawing lessons. haha.




This video is about an experiment, in the first few seconds,everything is normal then it became... well.... not normal . o-o

(PS:if you think this explnantion is too long and boring(i agree with myself) then you may want to look at the information(red in colour) below this.)



The center of gravity is also known as center of mass. The center of mass of a system of particles is a specific point at which, for many purposes, the system's mass behaves as if it were concentrated. The center of mass is a function only of the positions and masses of the particles that comprise the system. In the case of a rigid body, the position of its center of mass is fixed in relation to the object (but not necessarily in contact with it). In the case of a loose distribution of masses in free space, such as, say, shot from a shotgun, the position of the center of mass is a point in space among them that may not correspond to the position of any individual mass. In the context of an entirely uniform gravitational field, the center of mass is often called the center of gravity — the point where gravity can be said to act.
The center of mass of a body does not always coincide with its intuitive geometric center, and one can exploit this freedom. Engineers try to design a sports car's center of gravity as low as possible to make the car handle better. When high jumpers perform a "Fosbury Flop", they bend their body in such a way that it is possible for the jumper to clear the bar while his or her center of mass does not.
The so-called center of gravity frame (a less-preferred term for the center of momentum frame) is an inertial frame defined as the inertial frame in which the center of mass of a system is at rest.

this information has been taken from http://www.wikipedia.com/

In short , the center of gravity is a geometric property of any object. The center of gravity is the average location of the weight of an object. We can completely describe the motion of any object through space in terms of the translation of the center of gravity of the object from one place to another, and the rotation of the object about its center of gravity if it is free to rotate. If the object is confined to rotate about some other point, like a hinge, we can still describe its motion. In flight, both airplanes and rockets rotate about their centers of gravity. A kite, on the other hand, rotates about the bridle point. But the trim of a kite still depends on the location of the center of gravity relative to the bridle point, because for every object the weight always acts through the center of gravity.


this information is taken from: http://www.grc.nasa.gov/WWW/K-12/airplane/cg.html



now that you have endured these ''brain-killing lessons'' its....... comic time!

Scientists understood that the world was round, but in 1687, and English scientist named Isaac Newton explained why people do not fall off the earth. Newton realized that everything in the universe was attracted to everything else, and that the greater and closer the object, the greater its pull. We call this force gravity, which comes from a Latin word meaning heaviness. Everything and everybody has gravity-even you-but the earth has a mass of 5,972,000,000,000 pounds. The earth is very large, so people and objects are attracted to its gravitational pull. The earth orbits the sun because of the sun's gravitational pull on the earth.


Isaac newton knew this when he felt and apple drop/saw an aple drop on his head:












These are Newton's 3 laws of motion:
1:Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it.

2:For every action there is an equal and opposite reaction.

3:The relationship between an object's mass m, its acceleration a, and the applied force F is F = ma. Acceleration and force are vectors (as indicated by their symbols being displayed in slant bold font); in this law the direction of the force vector is the same as the direction of the acceleration vector.

Law 3 is the most important9as well as complicated law)
This is the most powerful of Newton's three Laws, because it allows quantitative calculations of dynamics: how do velocities change when forces are applied. Notice the fundamental difference between Newton's 2nd Law and the dynamics of Aristotle: according to Newton, a force causes only a change in velocity (an acceleration); it does not maintain the velocity as Aristotle held.

This is sometimes summarized by saying that under Newton, F = ma, but under Aristotle F = mv, where v is the velocity. Thus, according to Aristotle there is only a velocity if there is a force, but according to Newton an object with a certain velocity maintains that velocity unless a force acts on it to cause an acceleration (that is, a change in the velocity). As we have noted earlier in conjunction with the discussion of Galileo, Aristotle's view seems to be more in accord with common sense, but that is because of a failure to appreciate the role played by frictional forces. Once account is taken of all forces acting in a given situation it is the dynamics of Galileo and Newton, not of Aristotle, that are found to be in accord with the observations.

this explanation cwas taken from :http://csep10.phys.utk.edu/astr161/lect/history/newton3laws.html

Now here's a video of newton's 3 laws of motion
object :




(PS: you'll enjoy this video if you like listening to the mission impossible song, i can guarantee that :)
(PSS:look at the quicksand post and there'll be a new video, its called ''forest of death'', relax there's no horror scence, just people getting pulled by vines in quicksand:)

go to this website to watch the animation: http://regentsprep.org/Regents/physics/phys01/terminal/term3.htm

Terminal velocity is encountered any time you drive your car with a constant speed. The animation below shows the forces acting on a car starting from rest.

Be sure to watch the animation enough times to examine the following key concepts:
Initially, the applied force from the engine is the net force.
As the speed of the truck increases, the force of air friction (drag) also increases. The faster the car goes, the smaller the net force becomes.
Once the Fengine is cancelled out by the Fdrag, the net force is zero so there is no acceleration. The car moves with a constant velocity of 20 mph. 20 mph is the terminal velocity!