Tuesday, September 06, 2005
PHYSICS - Kinematics
HELLO KINEMATICS IS A SUPER SUPER SUPER IMPORTANT TOPIC. WITHOUT THIS TOPIC YOU WILL FAIL! Err whatever HAHA. But it's true! Because it is linked to forces and all that stuff so yeahh!
Okay first things first. FOUR VERY IMPORTANT EQUATIONS TO LEARN!!
a=(v-u)/t
s/t=(u+v)/2
v^2=u^2+2as
s=ut+0.5ut^2
where a=acceleration, v=final velocity, u=initial velocity, t=time and s=displacement
If you have a horribly lousy memory, DO NOT FRET! Because you actually just need to remember the first two formulae! If you happen to have a panic attack during the exam and forget the last two, just do SIMULTANEOUS EQUATIONS! And voila you get the next two equations. But of course if you can, just memorise everything so you don't waste time. (:
Okay now going back to basics.
1) Scalar quantities only require a magnitude.
2) Vector quantities require both a magnitude and direction.
Definitions:
Distance is the total length travelled by an object.
Displacement, however, is the LINEAR distance of the position of an object and direction from a given point! Thus it is possible for distance>0 and displacement=0.
Speed is the distance travelled per unit time.
Velocity is the displacement per unit time. The difference between velocity and speed is that it is possible for velocity to be negative but not speed. The explanation: Distance cannot be negative, but displacement can. Usually objects moving upwards and towards the right is having a POSITIVE displacement. (But in free fall acceleration going downwards is positive okay? (:)
Acceleration is the rate of change of velocity with regards to time. Thus it is also possible for acceleration to be negative. However, take note that deceleration/retardation is NOT the same as negative acceleration. Deceleration means that the object is slowing down, negative acceleration means that the object is travelling in a negative direction. (please correct me if i'm wrong, I'm not very sure about this point.) The acceleration due to free fall: g=10m/s^2 (the gravitational pull) In A levels they expect you to put g=9.81m/s^2! Okay haha random things.
There are basically 5 types of graphs they can test you on. Most common is velocity-time graph. The five graphs are:
1) Dist.-time graph
2) Disp.-time graph
3) Speed-time graph
4) Acceleration-time graph
5) Velocity-time graph
So be extra careful during the exam! Because if you don't read carefully and misinterpret the graph it's super wasted! Nods.
For the distance-time graph, the gradient=speed. Similarly for the displacement-time graph, the gradient=velocity. For speed-time graph and velocity-time graph, the gradient is the acceleration and the area under the graph is the distance/displacement. Lastly for the acceleration-time graph, the area under the graph is actually the average velocity/speed whatever.
HM! I guess..that's it. MMM I shall post another one on FORCES! Next post. :D
-- HH! ((:
Okay first things first. FOUR VERY IMPORTANT EQUATIONS TO LEARN!!
a=(v-u)/t
s/t=(u+v)/2
v^2=u^2+2as
s=ut+0.5ut^2
where a=acceleration, v=final velocity, u=initial velocity, t=time and s=displacement
If you have a horribly lousy memory, DO NOT FRET! Because you actually just need to remember the first two formulae! If you happen to have a panic attack during the exam and forget the last two, just do SIMULTANEOUS EQUATIONS! And voila you get the next two equations. But of course if you can, just memorise everything so you don't waste time. (:
Okay now going back to basics.
1) Scalar quantities only require a magnitude.
2) Vector quantities require both a magnitude and direction.
Definitions:
Distance is the total length travelled by an object.
Displacement, however, is the LINEAR distance of the position of an object and direction from a given point! Thus it is possible for distance>0 and displacement=0.
Speed is the distance travelled per unit time.
Velocity is the displacement per unit time. The difference between velocity and speed is that it is possible for velocity to be negative but not speed. The explanation: Distance cannot be negative, but displacement can. Usually objects moving upwards and towards the right is having a POSITIVE displacement. (But in free fall acceleration going downwards is positive okay? (:)
Acceleration is the rate of change of velocity with regards to time. Thus it is also possible for acceleration to be negative. However, take note that deceleration/retardation is NOT the same as negative acceleration. Deceleration means that the object is slowing down, negative acceleration means that the object is travelling in a negative direction. (please correct me if i'm wrong, I'm not very sure about this point.) The acceleration due to free fall: g=10m/s^2 (the gravitational pull) In A levels they expect you to put g=9.81m/s^2! Okay haha random things.
There are basically 5 types of graphs they can test you on. Most common is velocity-time graph. The five graphs are:
1) Dist.-time graph
2) Disp.-time graph
3) Speed-time graph
4) Acceleration-time graph
5) Velocity-time graph
So be extra careful during the exam! Because if you don't read carefully and misinterpret the graph it's super wasted! Nods.
For the distance-time graph, the gradient=speed. Similarly for the displacement-time graph, the gradient=velocity. For speed-time graph and velocity-time graph, the gradient is the acceleration and the area under the graph is the distance/displacement. Lastly for the acceleration-time graph, the area under the graph is actually the average velocity/speed whatever.
HM! I guess..that's it. MMM I shall post another one on FORCES! Next post. :D
-- HH! ((:
# we mugged! @ 5:08 AM 
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