Answer:
a)
b) For this case we can use this formula:
And replacinf for the runner B we got:
And the runner B should begin to run at:
Explanation:
For this case we have the following info given:
represent the initial velocity for runner A
represent the initial velocity for runner B
represent the difference of time between the two runners
represent the total distance for the exchange zone.
Part a
For this case we can use the following formula:
And we can define and we can convert this equation into:
And we can find the acceleration since we have all the other values like this:
And that would be the acceeleration for the runner A.
For the acceleration of the runner A we need to take in count that
And for this case we can use this:
And if we replace we got:
So for this case we have , and we can use this formula:
And solving for a we got:
Part b
For this case we can use this formula:
And replacinf for the runner B we got:
And the runner B should begin to run at: