Please give the diagram as well as the process.

Question

A river flows due north with a velocity of 3 km/h. A man rows a boat across the river with a velocity of 4 km/h relative to water due east. (a) What is his velocity relative to the earth?(b) If the river is 1km wide, how far north of his starting point will he reach the opposite bank?(c) How long a time is required to cross the river?

Answer 1

(i) Velocity of man relative to earth will be vector sum of velocity of ow of river and velocity of boat

(ii) Here, the man moves in the east direction with 4kmph and gets simultaneously 

Hence, if he travels x distance due east, in the same time he also travels 3x/4 distance due north. Given that x=1 km, thus 3x/4= 0.75 km 

(iii) The velocity of man in northward direction does not affect its speed in eastern direction which is 4km/h. Thus time taken = distance/speed ie 1/4 hrs = 15 min.