A boat crossing a wide river moves with a speed of 10 km/h relative to water. The water in the river has a uniform speed of 5.00 km/h due east relative to the Earth.

If the boat heads due north to the Earth, determine the velocity of the boat relative to an observer standing on either bank.
If the boat travels with the same speed of 10.0 km/h relative to the river and is to travel due north to the river, what should be its heading be?

Respuesta :

Answer:

Explanation:

Given

Boat travels with a velocity of 10\ kmph w.r.t water

i.e. [tex]v_{bw}=10\hat{j}[/tex]

Velocity of water w.r.t. earth [tex]v_{we}=5\hat{i}[/tex]Therefore velocity of boat w.r.t to earth is given by

[tex]v_{bw}=v_{be}-v_{we}[/tex]

[tex]v_{be}=v_{bw}+v_{we}[/tex]

[tex]v_{be}=10\hat{j}+5\hat{i}[/tex]

magnitude of velocity [tex]v=11.18\ m/s[/tex]

He traveling at an angle of

[tex]\tan \theta =\frac{v_x}{v_y}[/tex]

[tex]\tan \theta =\frac{5}{10}[/tex]

[tex]\theta =\tan ^{-1}(0.5)[/tex]

[tex]\theta =26.56^{\circ}[/tex] east of North

(b)Now if the Boat is travelling with a speed of 10 kmph w.r.t to river due to north

therefore he must leave with some angle west of north

i.e. Boat sin component will cancel the river velocity

[tex]v\sin \theta =5[/tex]

[tex]11.18\sin \theta =5[/tex]

[tex]\theta =26.55^{\circ}[/tex]

Therefore he should be heading towards [tex]26.55^{\circ}\ West\ of\ North\ with\ a\ velocity\ of\ 11.18\ m/s[/tex]

The velocity of the boat relative to an observer standing on either bank is 11.18 m/s.

The direction of the boat is 26.56⁰ North East.

Resultant velocity of the boat

The resultant velocity of the boat is determined as follows;

V² = V₁² + V₂²

V = √(V₁² + V₂²)

V = √(10² + 5²)

V = 11.18 m/s

Direction of the boat

The direction of the boat is calculated by applying trigonometry ratio.

tanθ = V₂/V₁

tanθ = 5/10

tanθ = 0.5

θ = tan⁻¹(0.5)

θ = 26.56⁰ North East.

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