Uniform Acceleration
The gradient of the velocity–time graph on page 40 has a constant value; it represents a constant or uniform acceleration. A number of equations link the variable quantities when an object is moving with uniform acceleration. They are:
- v = u + at
- s = ut + 1/2at2
- v2 = u2 + 2as
- s = 1/2(u + v)t
These equations involve a total of five variables but only four appear in each one, so if the values of three are known the other two can be calculated.
The symbols have the meanings already defined:
- u = initial velocity
- v = final velocity
- s = displacement
- a = acceleration
- t = time
When using the equations of uniformly accelerated motion:
- take care with signs; use + and – for vector quantities such as velocity and acceleration that are in opposite directions
- remember that s represents displacement; this is not the same as the distance travelled if the object has changed direction during the motion.
To work out the distance travelled by an object that changes direction, calculate the displacement both before and after the change in direction, and add these together.
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