Question

A boat is traveling upstream at 11 km/h with respect to thewater of a river. The water is flowing at 6.0 km/h with respect tothe ground. (a) What is the speed of the boat with respect to theground? (b) A child on the boat walks from front to rear at 6.0km/h with respect to the boat. What is the child's speed withrespect to the ground?

Answer 1

In this problem we taken the direction of the upstream istaken as positive.

So given that the speed of the boat relative to te wate ofriver is = 11km/s

   i.e.

velocity of water relative to the ground = 6.0km/h

   i.e.

Now

a)

Speed of the boat with respect to the ground is

     

           = (5.0km/h)i

The direction is along +X axis.

b)

Now the speed of the child with respect to the groundis

         

                =- (6.0km/h)i+(5.0km/h)i   

                = - (1.0km/h)i

Direction is along -X axis i.e downward stream.