Tuesday, September 06, 2005
PHYSICS - Forces
Yes, before I go on, just a reminder. TAKE NOTE OF SI UNITS AND SIGNIFICANT FIGURES DURING PHYSICS EXAM! :D
The SI unit for forces is Newton, or N. A force can be a push or a pull. A force can change the motion of an object (with regards to direction and acceleration) or even the shape of an object.
Newton has THREE laws of motion!
His first law of motion states that a body continutes in its state of rest or uniform motion in a straight line unless compelled by a force to do otherwise. In other words, F=0. Because in his SECOND law (see below), F=ma, and a=0 (: thus F=0. ER haha that's so bai chi. ._." Ahem. And the reluctance to change the state of motion (of an object) is called INERTIA. All objects with mass have inertia, even in OUTER SPACE! (should be. haha!)
ANYWAY! His second law states that the net force acting on an object=mass times acceleration of the object. In this case, for F=ma, F is the resultant force, not the applied force. From this formula, we can see that the weight is the mass times acceleration too, thus W=mg. yay.
Frictional force acts in the opposite direction of motion and when an object is stationary, there is no frictional force. If the applied force is less than the frictional force, the object would not move (duh haha).
Newton's third law of motion states that for everyaction there is an equal and opposite direction. For example, the centripetal and centrifugal force. The centripetal force is the force that pulls an object (which is moving around...something) towards the centre of the circle. By right there should be an equal and opposite force, and in this case it is the centrifugal force. However it only exists in theory, as there is really no such force. ._."
OOH A FUN FACT! (HAHA CORNY-NESS) Let me ask you. Why is there a need for a force which keeps the earth orbiting at a constant speed? Because. Well. Um since when the earth orbits, it keeps changing direction, so there will surely be acceleration. Thus there is a force NEEDED to keep the earth going at a constant speed. Imagine if the earth just kept accelerating. Then things would uh...start flying about! hahaha!
Things to note when drawing a force diagram (WREF):
Weight
Reaction force
External forces
Friction force
Now we go on to force diagrams and vector diagrams etc. There isn't much to learn here, because to excel at this drawing part you just need practise. Lots of it, if necessary. (: Once you get the hang of it, er...anyhow draw also can get the answer lah. Haha! Okay I think that's all for forces right? :D BYE!
-- HH! ((:
The SI unit for forces is Newton, or N. A force can be a push or a pull. A force can change the motion of an object (with regards to direction and acceleration) or even the shape of an object.
Newton has THREE laws of motion!
His first law of motion states that a body continutes in its state of rest or uniform motion in a straight line unless compelled by a force to do otherwise. In other words, F=0. Because in his SECOND law (see below), F=ma, and a=0 (: thus F=0. ER haha that's so bai chi. ._." Ahem. And the reluctance to change the state of motion (of an object) is called INERTIA. All objects with mass have inertia, even in OUTER SPACE! (should be. haha!)
ANYWAY! His second law states that the net force acting on an object=mass times acceleration of the object. In this case, for F=ma, F is the resultant force, not the applied force. From this formula, we can see that the weight is the mass times acceleration too, thus W=mg. yay.
Frictional force acts in the opposite direction of motion and when an object is stationary, there is no frictional force. If the applied force is less than the frictional force, the object would not move (duh haha).
Newton's third law of motion states that for everyaction there is an equal and opposite direction. For example, the centripetal and centrifugal force. The centripetal force is the force that pulls an object (which is moving around...something) towards the centre of the circle. By right there should be an equal and opposite force, and in this case it is the centrifugal force. However it only exists in theory, as there is really no such force. ._."
OOH A FUN FACT! (HAHA CORNY-NESS) Let me ask you. Why is there a need for a force which keeps the earth orbiting at a constant speed? Because. Well. Um since when the earth orbits, it keeps changing direction, so there will surely be acceleration. Thus there is a force NEEDED to keep the earth going at a constant speed. Imagine if the earth just kept accelerating. Then things would uh...start flying about! hahaha!
Things to note when drawing a force diagram (WREF):
Weight
Reaction force
External forces
Friction force
Now we go on to force diagrams and vector diagrams etc. There isn't much to learn here, because to excel at this drawing part you just need practise. Lots of it, if necessary. (: Once you get the hang of it, er...anyhow draw also can get the answer lah. Haha! Okay I think that's all for forces right? :D BYE!
-- HH! ((:
# we mugged! @ 5:28 AM 
