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A father is pulling his son on a sled at an angle of \(20^{\circ}\) with the horizontal with a force of 25 lb (see the following image). He pulls the sled in a straight path of 50 ft. How much work was done by the man pulling the sled? (Round the answer to the nearest integer.)

Short Answer

Expert verified
The work done is approximately 1175 ft-lb.

Step by step solution

01

Understand the Formula for Work

The formula for calculating work when force is applied at an angle is given by: \[W = Fd \cos(\theta)\]where \(W\) is the work done, \(F\) is the force applied, \(d\) is the distance, and \(\theta\) is the angle between the force and the direction of motion.
02

Identify the Given Values

From the problem, we are provided the following values: - Force \(F = 25\) lb- Distance \(d = 50\) ft- Angle \(\theta = 20^{\circ}\)
03

Substitute Values into the Formula

Substitute the given values into the work formula:\[W = 25 \times 50 \times \cos(20^{\circ})\]
04

Calculate the Cosine of the Angle

Calculate the cosine of \(20^{\circ}\):\[\cos(20^{\circ}) \approx 0.9397\]
05

Complete the Work Calculation

Now, substitute the calculated cosine value back into the formula and calculate:\[W = 25 \times 50 \times 0.9397 = 1174.625\]
06

Round the Answer to the Nearest Integer

Round the work done to the nearest integer:\[W \approx 1175\]

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Calculating Work
When we talk about calculating work in physics, we are referring to the process of determining how much energy is transferred when a force is applied to an object. The key formula for work is given by \[ W = Fd \cos(\theta) \]where:
  • \( W \) is the work done,
  • \( F \) is the magnitude of the force applied,
  • \( d \) is the distance through which the object moves, and
  • \( \theta \) is the angle between the force and the direction of motion.
To correctly calculate work, it is crucial to understand these components and their relationship to one another.
The formula reveals that work depends not only on the strength of the force and the distance moved but also on the angle between the force and the movement direction.
This angle is crucial because it determines how much of the force actually contributes to moving the object in the desired direction.
This explains why the cosine of the angle is used—cosine helps us project the force along the direction of motion, giving us the portion of the force that "counts" towards doing work.
Thus, by understanding how to calculate work, we can solve a wide range of problems involving energy transfer.
Forces and Angles
In physics, forces and angles play a significant role in determining how effectively work is done. A force can act in various angles relative to the direction of an object's movement, which impacts the amount of work performed.
For angles related to forces, here are a few key points to consider:
  • The angle \( \theta \) in the work formula represents the angle between the force and the direction of motion.
  • If \( \theta = 0^\circ \), the force is entirely in the direction of motion and delivers maximum work since \( \cos(0^\circ) = 1 \).
  • If \( \theta = 90^\circ \), the force is perpendicular to the direction of movement, meaning no work is done as \( \cos(90^\circ) = 0 \).
When a force is applied at an angle, only the component of this force that lies along the direction of motion will do work. The resultant effect is lessened by the angle of application due to the cosine factor.
In real-life situations, understanding the impact of forces and angles can help optimize efficiency and energy usage, for instance, when designing mechanisms or performing physical activities.
By using trigonometry, we can analyze these components and assess how they influence the work executed.
Physics Problem Solving
Physics problem solving is like piecing together a puzzle, requiring us to identify known quantities, apply relevant concepts, and carefully work through calculations. Using a systematic approach helps ensure nothing is overlooked.
Let's walk through a typical physics problem-solving strategy:
  • **Identify Given Values:** Begin by noting all known information like forces, angles, and distances.
  • **Understand the Formulas:** Use the applicable physics equations, such as the work formula \( W = Fd \cos(\theta) \), understanding each term’s contribution in the context.
  • **Substitute and Solve:** Plug in the known values for force, distance, and angle into the formula and perform the necessary calculations.
  • **Calculate Intermediate Steps:** Break it down, compute parts like \( \cos(\theta) \) separately if needed.
  • **Interpret and Rounding:** After calculation, interpret the result in the context of the problem and round to the required precision, if specified.
This structured approach gives clarity on the process, minimizes errors, and fosters a deeper understanding of the concepts at play.
With practice, students can become adept at dissecting complex problems through logical reasoning and precise calculations, leading to a stronger grasp of physics principles.

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