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Ch. 7 - Applications of Trigonometry and Vectors
Lial - Trigonometry 12th Edition
Lial12th EditionTrigonometryISBN: 9780136552161Not the one you use?Change textbook
Chapter 8, Problem 42

A force of 30.0 lb is required to hold an 80.0-lb pressure washer on an incline. What angle does the incline make with the horizontal?

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1
Identify the forces acting on the pressure washer on the incline: the weight (80.0 lb) acting vertically downward and the force required to hold it (30.0 lb) acting along the incline.
Recognize that the component of the weight acting parallel to the incline is balanced by the holding force. This component can be expressed as \(W \sin(\theta)\), where \(W\) is the weight and \(\theta\) is the angle of the incline.
Set up the equation relating the holding force to the component of the weight along the incline: \(30.0 = 80.0 \sin(\theta)\).
Solve for \(\sin(\theta)\) by dividing both sides of the equation by 80.0: \(\sin(\theta) = \frac{30.0}{80.0}\).
Find the angle \(\theta\) by taking the inverse sine (arcsin) of the value obtained: \(\theta = \arcsin\left(\frac{30.0}{80.0}\right)\).

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Resolving Forces on an Incline

When an object rests on an inclined plane, forces such as weight and applied force can be broken down into components parallel and perpendicular to the incline. Understanding how to resolve these forces helps analyze equilibrium and calculate unknown angles or forces.
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Example 2

Trigonometric Ratios (Sine, Cosine, Tangent)

Trigonometric ratios relate the angles of a right triangle to the ratios of its sides. In problems involving inclines, sine, cosine, and tangent functions are used to connect the incline angle with force components, enabling calculation of unknown angles or lengths.
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Sine, Cosine, & Tangent of 30°, 45°, & 60°

Equilibrium of Forces

An object in equilibrium has net forces equal to zero. For the pressure washer held stationary on the incline, the applied force balances the component of its weight along the incline. Applying equilibrium conditions allows solving for the incline angle.
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