PH1 Kinematics
UVAXT Equations
Vectors & Scalars
Vectors
e.g. displacement, velocity
have a direction, and a
magnitude, are a
straight line.
e.g. 3ms-1 to the East
Scalars
e.g. distance, speed
have magnitude, can be
along a non-straight
line.
e.g. the car travelled
1425m from door-todoor
Vectors & Scalars
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Distance & Displacement
Speed or Velocity?
Units
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Distance/displacement: meters (m)
Speed/Velocity – distance moved per second
= (meters) per second (m/s or ms-1)
Acceleration – change in speed per second
= (meters per second) per second
= (m/s)/s
= m/s2 or ms-2
Velocity-time graphs
velocity
v
Gradient = acceleration
u
Area = displacement
t
time
Other graphs
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Displacement-Time:
gradient = instantaneous velocity
Acceleration-Time:
area underneath = final velocity
Now try some questions…
UVAXT equations
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v = u + at
x = ut + ½at2
x = vt – ½at2
v2 = u2 + 2ax
x = ½(u+v)t
Only when a
is constant!
Questions
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From the worksheet:
UVAXT Questions
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Work out initial conditions
Find out which quantity you are calculating
Find out which quantity you don’t need.
Identify the correct equation
Do the maths
Example
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A car accelerates from
rest at 0.4ms-2 for 15s.
How far does it go?
U
0

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V
A
0.4
X
T
?
15
x = ut + ½at2
x = (0)(15) + 0.5(0.4)152
= 45m
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Work out initial
conditions
Find out which quantity
you are calculating
Find out which quantity
you don’t need.
Identify the correct
equation
Do the maths
You may need the square root formula
ax  bx  c  0
2
 b  b  4ac
x
2a
2
2 volunteers needed
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… for a demo next lesson