Finding Magnitude of Two Forces

PhysicsVector MechanicsMediumSTEM

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Two forces acting at a point are inclined $55^{\circ}$. The magnitude of one force is five over two times the other. If the resultant is $25\text{N}$, find the magnitude of each force.

Animated Video Solution

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Step by Step Written Solution

1
Step 1

Hi shama, let's solve this together. We need to find the magnitudes of two forces acting at a point given their relative magnitude, the angle between them, and the magnitude of their resultant force.

Problem Analysis

- Angle between forces $\theta = 55^\circ$

- Resultant force $R = 25 \text{ N}$

- One force is five over two times the other

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Step 2

Let's represent the magnitude of the smaller force as F sub one, and the larger force as F sub two.

$$F_1 = F$$
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Step 3

Since the magnitude of one force is five over two times the other, we can write F sub two as two point five times F sub one.

$$F_2 = \frac{5}{2} F_1 = 2.5 F_1$$
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Step 4

Now, let's recall the formula for the magnitude of the resultant of two forces acting at an angle theta.

The Resultant Force Formula

$$R^2 = F_1^2 + F_2^2 + 2 F_1 F_2 \cos \theta$$
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Step 5

Let's substitute F sub two equals two point five times F sub one into our formula.

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Step 6

We can simplify this by squaring two point five and multiplying two by two point five.

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Step 7

Now, let's factor out F sub one squared from all the terms on the right-hand side.

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Step 8

Next, let's calculate the numerical terms inside the parentheses. We start with the value of cosine fifty-five degrees.

Evaluating Coefficients

$$\cos 55^\circ \approx 0.5736$$

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About This Question

Subject
Physics
Topic
Vector Mechanics
Difficulty
Medium
Exam
STEM
Question Type
Open Ended

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