A river flows at 2.50 m/s to the north, while a boat travels from south to north with a
constant velocity of 12.5
m/s relative to the water.
What is the velocity of the boat relative to an
observer at rest on the shore?

15 m/s towards the North

Explanation:

we need to add both velocities to find the effective velocity from the point of view of an observer at rest on the shore:

2.5 m/s + 12.5 m/s = 15 m/s pointing North

the first american roller coaster was the mauch chunk switchback railway, built in the mountains of pennsylvania in the mid-1800s. the track, originally built to send coal to a railway, was reconfigured as a "scenic tour."

need to see circuit to get time constant