PHYSICS- kinematics

kinematics

key words:- displacement: distance moved in a particular direction- speed: average speed is distance moved in time taken- mean speed: total distance traveled over total time taken- acceleration: the rate of change of velocity (rate means divided by time)- velocity: speed of something in a given direction- instantaneous speed: value of the speed off an object at a particular time                    if a question said " determine the speed at 6.0s " you would draw a tangent at that point and work out the speed                    by using change in y/ change in CHANGE IN DIRECTION > CHANGE IN VELOCITY > CHANGE IN ACCELERATION+ A change in speed, direction means that the object has a change in velocity+ in physics if you turn a corner , and your speed is constant-- your velocity still changes.+ To maximize your velocity you displace more from your original position

distance time graph

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speed time graphs

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method for working out instantaneous acceleration:>draw a tangent at a specific point=change in y/change in xthe gradient will be the accelerationMethod for working out the distance travelled >area under the curveX x Y/2 (for a triangle)X x Y (for a rectangle)speed x time = distance 

displacement time graphs

displacement is the distance of how far the object has moved from the original positiona displacement time graph represents how the position of an object relative to a fixed position changes as time progresses~the gradient of a displacement time graph is VELOCITY A d-t is a curveThe area under the curve has no meaningit shows the amount it has displaced from its original position, even if it is going towards the position it is still displacing itself. 

velocity time graphs

The gradient of a velocity time graph is ACCELERATION>the steeper the slope the higher acceleration>FORWARDS (positive numbers)- if the slope is + its accelerating                                                          - if the slope is - its decelerating>BACKWARDS(negative numbers)-if the slope is + its                                                                                    decelerating                                                             - if the slope is -, it is                                                                                  accelerating>CHANGES DIRECTION WHEN IT CROSSES X AXIS

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acceleration time graphs

logic that all freely falling objects ( in the absence of air resistance) accelerate to earth with the same acceleration.  ACCELERATION DUE TO GRAVITY- 9.1ms-1

equations of motion

~~ these are only used when acceleration is constant~~Acceleration = change in velocity                                time taken A=V-U       TWe can rearrange this formula to make V the subject of the formulaV= U + ATthe area under the curve is DISPLACEMENT=(area of trapezium)S= 1 ( U + V ) x T     2

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equations of motion...

we can combine      V = U + AT  and  S = 1 ( U + V ) x T                                         2substitute v= u + at into the other formulaS = 1 (U + U + AT) x T      2S = 1 (2U + AT) x T       2S = 1 (2U + AT ^2)             S = 1 2 UT + 1 AT^2       2                                          2             2S= UT + 1 AT ^2               2

now we can combine   S= UT + 1 AT ^2                                                 2and V = U + AT to make   V^2 = U^2+ 2ASV^2 = (U + AT)^2        = U^2 + 2U AT + A^2 T^2        = U^2 +2A( UT +1/2 AT^2)        = U^2 +2ASV= FINAL VELOCITYU= INITIAL VELOCITYA= ACCELERATIONS= DISPLACEMENTT= TIME

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S.U.V.A.T

SUVAT is a technnique used that applies all the four different equations of motion S= dislacement (m) sometimes called X in examsU= inital speed (ms-1)V= final speed (ms-1)A= acceleration (ms-2)T= time (s)

vertical motion under gravity

converting from v-t to d-t graphs

on a velocity time graph when it passes through the origin it means it chnaged direction BUT on a d-t graph it doesnt matter if it changes direction it is still moving and accelerating. >if it is decelerating the curve on the d-t graph will just flatten out