Jenny and alyssa are members of the cross-country team. on a training run, jenny starts off and runs at a constant 3.8 m/s. alyssa starts 15 s later and runs at a constant 4.0 m/s. at what time after jenny's start does alyssa catch up with jenny?

285 seconds

Explanation:

Jenny speed is 3.8 m/s

Alyssa speed in 4.0 m/s

Alyssa starts after 15 seconds

Find the distance covered by Jenny, when Alyssa starts

Distance=Speed*time

Distance covered by Jenny in 15 seconds= 3.8×15=57m

Relative speed of the two members heading same direction will be;

4.0m/s-3.8m/s=0.2m/s

To find the time Alyssa catch up with Jenny you divide the distance to be covered by Alyssa by the relative speed of the two

Distance=57m, relative speed=0.2m/s  t=57/0.2 =285 seconds

=4.75 minutes

Explanation:

, because she has a difference of 15 seconds.

Both move at a constant speed, that means there's no acceleration, their speed is always the same.

Now, the equation of each movement is

and , then we solve this two.

We replace the first equation into the second one

That means after 100 seconds Alyssa catch up with Jenny.

reserve is the answer