Phy Motion question (eng)

Given,
Speed = 10.5 m/s
Time used = 3 min = 180 sec
Radius of Track = 400 m

Therefore, distance travelled = 10.5 x 180 = 1890 m
Since this is an arc length, the movement in angular term is:
1890/400 = 4.725 rad

So the displacement (linear distance between the two points) is:
400 * 2 * sin[(2pi - 4.725)/2]
=562.1073

And velocity = 562.1073/180 = 3.12 m/s


Note (use approximations to the solution):
The angular movement 4.725 rad is close to 270°
If Marilyn start at N, then the stopping point will be at E
Since it is a circular track, the final point is S45°E from starting point.
With a 90° angle of both sides 400m, the displacment is [(400^2) + (400^2)]^(1/2)
= 565.6854 m
Velocity = 3.14 m/s