Question

A 0.14-km wide river flows with a uniform speed of 4.0 m/s toward the east. It takes 20 s for a boat to cross the river to a point directly north of its departure point on the south bank. What is the speed of the boat relative to the water

Answer 1

The right approach is "8.1 m/s". A further explanation is provided below.

Step-by-step explanation:

According to the table,

Speed of Boat

=
`(s)/(t)`

`V_b=(140)/(20)`

`V_a = 4 \ m/s`

`V_B = 7 \ m/s`

Now,

⇒
`(V_(relative))^2 = (7)^2+(4)^2`

or,

⇒
`(V_r)^2=49+16`

`=65`

`V_r=√(65)`

`=8.1 \ m/s`