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Kinematics (Speed, distance & acceleration (Acceleration: (the rate of…
Kinematics
Speed, distance & acceleration
Distance:
The total length of a journey travelled
Speed:
the rate of change of distance
distance / time
Acceleration:
the rate of change of speed
speed / time
*actually a vector – should be velocity
'Instantaneous' measurement
Measured at a specific point in time
Only valid at that instant
'Average' measurement:
Calculated over the entire journey
eg. av. speed = total d / total t
Constant acceleration formulae (suvat equations)
If acceleration is constant, there are 5 key quantities that define an object's motion
s - displacement
u - initial velocity
v - final velocity
a - acceleration
t - time
Equations
a = (v-u)/t
s = ut + 1/2 • at^2
s = vt - 1/2 • at^2
v^2 = u^2 + 2as
s = (u+v)/2 • t
Solving problems
Convert where needed into SI units
Write down the 3 known suvat quantities, and the one we want to find
Choose appropriate equation from the above
Substitute into the equation
Vector or Scalar
Scalar quantities describe
magnitude
Distance
Speed
Vector quantities describe
magnitude and direction
Displacement
Velocity
Graphs
Gradient – rate of change of:
Displacement-time graph – velocity
Velocity-time graph – acceleration
Area – total change in:
Acceleration-time graph – velocity
Velocity-time graph – displacement