MCQEasyJEE 2023Vector Addition & Resolution

JEE Mathematics 2023 Question with Solution

A vector in the xyx–y plane makes an angle of 3030^\circ with the yy-axis. The magnitude of the yy-component of the vector is 232\sqrt{3}. The magnitude of the xx-component of the vector will be

  • A

    22

  • B

    3\sqrt{3}

  • C

    13\dfrac{1}{\sqrt{3}}

  • D

    66

Answer

Correct answer:A

Step-by-step solution

Standard Method

Given: A vector makes an angle of 3030^\circ with the yy-axis, and its yy-component is 232\sqrt{3}.

Find: The magnitude of the xx-component.

If a vector of magnitude VV makes an angle θ\theta with the yy-axis, then

y-component=Vcosθ,x-component=Vsinθy\text{-component} = V\cos\theta, \quad x\text{-component} = V\sin\theta

Using the given values,

Vcos30=23V\cos 30^\circ = 2\sqrt{3}

Since

cos30=32\cos 30^\circ = \frac{\sqrt{3}}{2}

we get

V32=23V \cdot \frac{\sqrt{3}}{2} = 2\sqrt{3}

Cancelling 3\sqrt{3},

V2=2V=4\frac{V}{2} = 2 \Rightarrow V = 4

Now the magnitude of the xx-component is

x-component=Vsin30=412=2x\text{-component} = V\sin 30^\circ = 4 \cdot \frac{1}{2} = 2

Therefore, the magnitude of the xx-component is 22. The correct option is A.

Component Ratio Trick

Given: The angle is measured from the yy-axis.

Find: The xx-component.

When the angle is measured from the yy-axis,

x-componenty-component=tanθ\frac{x\text{-component}}{y\text{-component}} = \tan \theta

So,

x23=tan30=13\frac{x}{2\sqrt{3}} = \tan 30^\circ = \frac{1}{\sqrt{3}}

Hence,

x=2313=2x = 2\sqrt{3} \cdot \frac{1}{\sqrt{3}} = 2

Therefore, the magnitude of the xx-component is 22.

Common mistakes

  • Using x=Vcosθx = V\cos\theta and y=Vsinθy = V\sin\theta as if the angle were measured from the xx-axis. This is wrong because the given angle is with the yy-axis. Use y=Vcosθy = V\cos\theta and x=Vsinθx = V\sin\theta instead.

  • Treating the given 232\sqrt{3} as the vector magnitude instead of the yy-component. This is wrong because the problem explicitly gives only one component. First find VV or use the component ratio correctly.

Practice more Vector Addition & Resolution questions

Get unlimited AI-adaptive practice, mastery tracking, and an AI tutor that explains every step — free to start.