Question

Your English teacher can swim with a constant speed of 0.67m/s. While facing south , he attempts to swim straight across the St. Lawrence River , which moves east at 1.4 m/s
a) find his velocity as seen from the riverbank.

B) if the river was 175m wide
How long does it take him to cross the
River



Hri

Answer 1

teacher: v1=0.67 m/s,
river: v2 =1.4 m/s,
v=sqrt(v1²+v2²) =1.55 m/s. (to the east of south)
L =175 m,
s=?
v/v1=s/L =>
s= v•L/v1 =1.55•175/0.67 =404 m.
t=s/v =404/1.55 =260 s =4.34 min