Question Details

The magnitude and direction of the acceleration produced in a body of mass 5 kg when two mutually perpendicular forces 8 N and 6 N act on it, are respectively:

Options

A

2 m s−2;tan−1(4/3) with 8 N force

B

2 m s−2;tan−1(3/4) with 8 N force

C

2 m s−2;tan−1(3/4) with 6 N force

D

20 m s−2;tan−1(4/3) with 8 N force

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Correct Answer :

Option B

2 m s−2;tan−1(3/4) with 8 N force

2 m s⁻²; tan⁻¹(3/4) with 8 N force

Solution :

First, resolve the two perpendicular forces into orthogonal components. Let the 8 N force act along the x‑axis and the 6 N force act along the y‑axis.

Calculate the magnitude of the resultant force using the Pythagorean theorem:

F_{\text{result}} = \sqrt{8^{2} + 6^{2}} = \sqrt{64 + 36} = \sqrt{100} = 10\ \text{N}

Now apply Newton’s second law, \(\mathbf{F}=m\mathbf{a}\), to find the magnitude of the acceleration:

a = \frac{F_{\text{result}}}{m} = \frac{10\ \text{N}}{5\ \text{kg}} = 2\ \text{m·s}^{-2}

Next, determine the direction of the acceleration relative to the 8 N force (the x‑axis). The angle \(\theta\) satisfies

\tan\theta = \frac{6}{8} = \frac{3}{4}

Hence

\theta = \tan^{-1}\!\left(\frac{3}{4}\right)

This angle is measured from the direction of the 8 N force toward the 6 N force.

Therefore, the acceleration of the 5 kg body has a magnitude of 2 m·s⁻² and is directed at an angle \(\tan^{-1}(3/4)\) measured from the line of action of the 8 N force.

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