Answer:
1) 
2) 
3) 

Explanation:
Given:
width of river, 
speed of stream with respect to the ground, 
speed of the swimmer with respect to water, 
<u>Now the resultant of the two velocities perpendicular to each other:</u>



<u>Now the angle of the resultant velocity form the vertical:</u>



- Now the distance swam by the swimmer in this direction be d.
so,



Now the distance swept downward:



2)
On swimming 37° upstream:
<u>The velocity component of stream cancelled by the swimmer:</u>



<u>Now the net effective speed of stream sweeping the swimmer:</u>



<u>The component of swimmer's velocity heading directly towards the opposite bank:</u>



<u>Now the angle of the resultant velocity of the swimmer from the normal to the stream</u>:



- Now let the distance swam in this direction be d'.



<u>Now the distance swept downstream:</u>



3)
Time taken in crossing the rive in case 1:



Time taken in crossing the rive in case 2:



Answer
mass of a person is 80 kg
a) Mexico City, Mexico
acceleration due to gravity in mexico = 9.776 m/s²
weight = 80 × 9.776 = 782.08 N
b) Cape Town, South Africa
acceleration due to gravity in cape town = 9.796 m/s²
weight = 80 × 9.796 = 783.68 N
c) Tokyo, Japan
acceleration due to gravity in cape town = 9.798 m/s²
weight = 80 × 9.798 = 783.84 N
d) Chicago, IL
acceleration due to gravity in cape town = 9.803 m/s²
weight = 80 × 9.803 = 784.24 N
e) Copenhagen, Denmark
acceleration due to gravity in cape town = 9.815 m/s²
weight = 80 × 9.815 = 785.2 N
D) the temperature of the water will start to drop after climbing.