Amy is paddling her canoe across a lake at a speed of 10 feet per second headed due north. The wind is blowing 40°C east of north with a velocity of 2.8 feet, per second. What is Amy's resultant velocity? Express your answer as a vector. Show your work.

Respuesta :

The resultant velocity is about 12.3 feet per second at a heading of 8.4°east of north, <1.8, 12.14>

In this question,

Amy is paddling her canoe across a lake at a speed of 10 feet per second headed due north.

The wind is blowing 40°C east of north with a velocity of 2.8 feet, per second.

We need to find Amy's resultant velocity.

We write the direction vector for Amy in component form.

Due north is equivalent to 90° from the horizontal.

x-component:

x = 10 cos(90°)

x = 0

And y-component:

y = 10 sin(90°)

y = 10

The component form for Amy’s vector is <0, 10>.

Now we write the direction vector for wind in component form.

40 east of north is equivalent to 50° from the horizontal.

x-component:

x = 2.8 cos(50°)

x = 1.8

And y-component:

y = 2.8 sin(50°)

y = 2.14

The component form for the wind’s vector is <1.8, 2.14>

Add the vectors for Amy and the wind.

<0, 10> + <1.8, 2.14> = <1.8, 12.14>

Now, we determine the vector's magnitude by using Pythagoras theorem.

Let v be the velocity of Amy.

Let θ be the angle made by Amy with the horizontal

⇒ tan(θ) = |y/x|

⇒ tan(θ) = |12.14 / 1.8|

⇒ θ = 81.6°

81.6° with the horizontal is equivalent to 8.4° east of north.

Therefore, the resultant velocity is about 12.3 feet per second at a heading of 8.4°east of north, <1.8, 12.14>

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