How do you calculate final speed?

Question

My teacher only taught us how to calculate average speed.
A runner, starting from a state of rest runs a distance of 30m in 3.5s.
a) How would you calculate his final speed.
b) Calculate his final speed.

Pearlsawme · Accepted Answer

Average speed is the actual distance traveled / total time of travel .

If the speed increases UNIFORMLY one can find the average velocity by adding the initial and final speed and then dividing it by two.

Hence in this case 

(u + v) / 2 = distance / time = 30 / 3.5 = 8.57 m/s which is the average speed 

Since the initial speed is zero 

(0 + v) /2  = 8.57 

v = 17.14 m/s  Final speed 

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Note when an object starts from rest , final speed is twice the average speed.
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Justin · Answer

They are the same thing in this example.  Just put the average speed.
Speed = distance / time
S = D/t
S = 30 /3.5
S = 60/7 meters per second
S = 8 +(4/7) m/s

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How do you calculate final speed?

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