Acceleration

== =Acceleration= Acceleration - The quantity that describes the rate of change of velocity in a given time interval; how fast velocity changes; D Velocity / DT ime Acceleration is usualy written in meters per second per second (m/s²); note that this can also be written as (m/s/s).

D Velocity = Vf - Vi D Time = Tf - Ti

=Velocity vs Time Graph= - A graph that shows an objects velocities at certain points in time. Þ The slope of a velocity versus time graph represents the objects acceleration. When the slope is positive the object is speeding up. The object is slowing down when the slope is negative. However, this is only true in quadrant I (+,+) of a graph because in quadrant IV (+,-) where the velocities are negative this is reversed. It is impossible to include quadrants II (-,+) and III (-,-) because negative time cannot be acheived. Also, undefined slopes (vertical lines) are physically impossible because the object can only have one velocity at any given time. A Horizontal slope, however, can exist; This only means the object's velocity is not changing and it's acceleration is 0.

Graph Description: Constant Acceleration; Slope = 2 = Acceleration = 2(m/s²) Velocity is changing by the slope, 2(m/s²), every equal time interval In this case it is increacing. Displacement is increacing every equal time interval. This is shown in the graph below.

=Acceleration Examples:= How fast a car is speeding up. How fast a train is becoming faster. What happens when you slam your foot on the pedal real hard.

=Freefall Acceleration:= Acceleration is constant when an object is in freefall. This means that velocity changes by the same amount each second during freefall. Þ The acceleration of an object in freefall is always 9.8(m/s²), which is 20(mph). Þ The mass of the object does not change the objects acceleration during freefall.

=Graph of an object in freefall (Up and Down Motion):= Þ The object starts moving upwards. Then at the apex of the blue line it begins moving downward. Graph Description: The acceleration or green line does not change. This is because the object is in freefall when velocity changes by -9.8(m/s/s). Þ The object starts with a speed of 25(m/s). It is slowing down as the object moves upwards. Þ The blue line represents the position of the object. Therefore the objects highest point is 30(m). This is because the line does not go above 35(m). At that point, 35(m), the object is not moving; its speed is 0. This is the point where the object stops moving upwards and starts going downwards. Þ At the end, when the graph stops the objects speed is 25(m/s). The object was speeding up as it came downwards.

=NOTE:= The average acceleration of an object that has constant acceleration is equal to it's acceleration at any given point in time. Þ If the change in velocity is negative; the acceleration will also be negative. However, if the change in veloctiy is positive acceleration will also be positive. Þ If a shuttle bus deccelerated any faster the people inside would be pushed in the direction the shuttle bus was moving. This is because the people don't have breaks lowering their acceleration too.