/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 73 You are in your car driving on a... [FREE SOLUTION] | 91Ó°ÊÓ

91Ó°ÊÓ

You are in your car driving on a highway at 25 \(\mathrm{m} / \mathrm{s}\) when you glance in the passenger side mirror (a convex mirror with radius of curvature 150 \(\mathrm{cm}\) ) and notice a truck approaching. If the image of the truck is approaching the vertex of the mirror at a speed of 1.5 \(\mathrm{m} / \mathrm{s}\) when the truck is 2.0 \(\mathrm{m}\) away, what is the speed of the truck relative to the highway?

Short Answer

Expert verified
The truck's speed relative to the highway is 14.33 m/s.

Step by step solution

01

Understand the Problem

We need to find the speed of the truck relative to the highway. We know the truck is moving towards a convex mirror such that its image approaches the mirror at 1.5 m/s. The mirror has a radius of curvature of 150 cm, which is 1.5 m.
02

Use Mirror Formula

For a convex mirror, the mirror formula is \(\frac{1}{f} = \frac{1}{d_o} + \frac{1}{d_i}\), where \(f\) is the focal length, \(d_o\) is the object distance, and \(d_i\) is the image distance. The focal length \(f\) is half of the radius of curvature, so \(f = -\frac{1.5}{2} = -0.75\, \text{m}\).
03

Find Image Distance

Given \(d_o = 2.0\, \text{m}\) and \(f = -0.75\, \text{m}\), use the mirror formula: \[\frac{1}{-0.75} = \frac{1}{2.0} + \frac{1}{d_i}\].Solve for \(d_i\): \[\frac{1}{d_i} = \frac{1}{-0.75} - \frac{1}{2.0}\] \[\frac{1}{d_i} = -\frac{4}{3} - \frac{1}{2} = -\frac{8}{6} - \frac{3}{6} = -\frac{11}{6}\]\[d_i = -\frac{6}{11} \approx -0.545\, \text{m}\].
04

Use Ratios to Find Truck Speed

The rate at which the image distance \(d_i\) changes is related to the rate at which the object distance \(d_o\) changes. Using the relationship: \[\frac{\Delta d_i}{\Delta t} = \left(-\frac{f^2}{d_o^2}\right)\frac{\Delta d_o}{\Delta t},\]where \(\frac{\Delta d_i}{\Delta t} = 1.5\, \text{m/s}\). Find \(\Delta d_o / \Delta t\) by rearranging: \[1.5 = \frac{\left(-0.75\right)^2}{2^2} \times (-v)\] \[1.5 = \frac{0.5625}{4} \times (-v)\]\[v = \frac{1.5}{0.140625} = 10.67\, \text{m/s}\].
05

Find Relative Speed

The truck’s speed relative to the highway is the speed of the car (25 m/s) minus the speed of the truck relative to the mirror (10.67 m/s): \[v_{\text{truck}} = 25 - 10.67 = 14.33\, \text{m/s}.\]

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Over 30 million students worldwide already upgrade their learning with 91Ó°ÊÓ!

Key Concepts

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

Optics
Optics is a branch of physics focused on the behavior and properties of light. This exciting field explores how light interacts with different materials—something crucial to understanding mirrors and lenses. When it comes to mirrors, there are different types including plane, concave, and convex mirrors. Convex mirrors, like those used in car passenger side mirrors, are designed with a surface that bulges outward. This design allows for a wider field of view, making it easier to see more of the road. However, it also causes images to appear smaller and further away than they actually are. Understanding these basic optics principles is essential for solving physics problems involving mirrors.

By comprehending how light is reflected in a convex mirror, you can predict how images will behave. This knowledge can be applied to find answer to questions pertaining to relative velocities and positions of objects like cars and trucks.
Relative Velocity
Relative velocity is a concept that is used to describe the velocity of one object as observed from another object. In the context of this exercise, we are dealing with the relative velocity between a moving truck and a car. The key is to calculate how fast the truck is moving from the perspective of a mirror mounted on a car traveling at a constant speed on the highway.

It’s important to note that the velocity measured can either be towards or away from the observer. This concept of relative velocity helps in understanding not just how fast, but in what direction an object is moving relative to another. In this specific problem, the truck is moving towards both the mirror and car and we’re initially given the rate at which the truck's image approaches the mirror.
  • It's crucial to differentiate between absolute velocity (speed relative to the ground) and relative velocity (speed relative to a moving frame like a car).
  • These calculations can assist in adjusting speeds safely while driving or in engineering scenarios.
Physics Problem Solving
Tackling physics problems often involves breaking down a complex problem into simple, manageable pieces. This structured approach ensures clarity and enhances understanding. Start by clearly identifying what you’re given in a problem and what you need to find. In this exercise, it's crucial to first determine the speed of the truck, considering both its movement towards the mirror and relative to the highway.

By dissecting the exercise into steps, like using the mirror formula and calculating relative velocity, you can effectively handle multi-step computations. Problem-solving in physics can involve utilizing formulas, making logical assumptions, and connecting various laws of physics. These processes not only help solve the problem at hand but also build a stronger foundational understanding which is applicable to a range of scenarios.

A comprehensive problem-solving strategy typically includes:
  • Understanding the problem
  • Extracting necessary formulas
  • Performing calculations step-by-step
  • Reviewing the solution for consistency and accuracy
Mirror Formula
The mirror formula is an essential equation in optics that relates object distance, image distance, and focal length, especially when considering curved mirrors. For a convex mirror, the mirror formula is given by \[\frac{1}{f} = \frac{1}{d_o} + \frac{1}{d_i}\].

This formula helps determine the position of the image formed by a mirror based on the position of the object and the mirror's focal length. In this exercise, we have a convex mirror, which results in a negative focal length. The radius of curvature is twice the focal length, helping solve for the image distance through calculation.

By inserting the known values into the mirror formula, we can identify the distance of the image—and by extension, infer various other properties, such as size and orientation. Understanding the mirror formula and its application helps unravel how images form and behave, proving crucial for accurately tackling related physics problems.

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

A layer of benzene \((n=1.50) 2.60 \mathrm{cm}\) deep floats on water \((n-1.33)\) that is 6.50 \(\mathrm{cm}\) deep. What is the apparent distance from the upper benzene surface to the bottom of the water layer when it is viewed at normal incidence?

Resolution of a Microscope. The image formed by a microscope objective with a focal length of 5.00 \(\mathrm{mm}\) is 160 \(\mathrm{mm}\) from its second focal point. The eyepiece has a focal length of 26.0 \(\mathrm{mm}\) . (a) What is the angular magnification of the microscope? (b) The unaided eye can distinguish two points at its near point as separate if they are about 0.10 \(\mathrm{mm}\) apart. What is the minimum separation between two points that can be observed (or resolved) through this microscope?

You have a camera with a 35.0 -mm focal length lens and 36.0 -mm-wide film. You wish to take a picture of a 120 -m-long sailboat but find that the image of the boat fills only \(\frac{1}{4}\) of the width of the film. (a) How far are you from the boat? (b) How much closer must the boat be to you for its image to fill the width of the film?

Three-Dimensional Image. The longitudinal magnification is defined as \(m^{\prime}=d s^{\prime} / d s .\) It relates the longitudinal dimension of a small object to the longitudinal dimension of its image. (a) Show that for a spherical mirror, \(m^{\prime}=-m^{2}\) . What is the significance of the fact that \(m^{\prime}\) is always negative? (b) A wire frame in the form of a small cube 1.00 \(\mathrm{mm}\) on a side is placed with its center on the axis of a concave mirror with radius of curvature 150.0 \(\mathrm{cm}\) . The sides of the cube are all either parallel or perpendicular to the axis. The cube face toward the mirror is 200.0 \(\mathrm{cm}\) to the left of the mirror vertex. Find (i) the location of the image of this face and of the opposite face of the cube; (ii) the lateral and longitudinal magnifications; (iii) the shape and dimensions of each of the six faces of the image.

You are examining an ant with a magnifying lens that has focal length 5.00 \(\mathrm{cm}\) . If the image of the ant appears 25.0 \(\mathrm{cm}\) from the lens, how far is the ant from the lens? On which side of the lens is the image located?

See all solutions

Recommended explanations on Physics Textbooks

View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.