Question

A boat moving at 7.8 km/hr relative to the water is crossing a river 3.5 km wide in which the current is flowing at 2.8 km/hr. At what angle upstream should the boat head to reach a point on the other shore directly opposite the starting point?

Answer 1

Answer:
`\theta =21.03^(\circ)`

Step-by-step explanation:

Given

velocity of boat with respect to river
`=7.8 km/hr`

velocity of river is
`2.8 km/hr`

River is 3.5 km wide

Suppose boat leaves at an angle of
`\theta` with vertical such that it reaches exactly opposite end of initial Point

Therefore

`7.8\sin \theta`component will balance the river Flowso that sin component helps to cross the river

`7.8\sin \theta =2.8`

`\sin \theta =0.3589`

`\theta =sin^(-1)(0.3589)`

`\theta =21.03^(\circ)`