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In a historical movie, two knights on horseback start from rest \(88.0 \mathrm{~m}\) apart and ride directly toward each other to do battle. Sir George's acceleration has a magnitude of \(0.300 \mathrm{~m} / \mathrm{s}^{2},\) while Sir Alfred's has a magnitude of \(0.200 \mathrm{~m} / \mathrm{s}^{2}\). Relative to Sir George's starting point, where do the knights collide?

Short Answer

Expert verified
The knights collide 52.8 meters from Sir George's starting point.

Step by step solution

01

Understand the Problem

Two knights are accelerating towards each other, starting 88 meters apart. We need to find the location of their collision relative to Sir George's start.
02

Relevant Formulas

Use the formula for distance when an object accelerates from rest: \( s = \frac{1}{2} a t^2 \), where \( s \) is the distance traveled, \( a \) is the acceleration, and \( t \) is time.
03

Define the Variables

Let \( s_G \) be the distance Sir George travels and \( s_A \) be the distance Sir Alfred travels until they collide. The equation \( s_G + s_A = 88 \) describes their combined travel distance.
04

Set Up the Equations

For Sir George: \( s_G = \frac{1}{2} \times 0.300 \times t^2 = 0.15t^2 \). For Sir Alfred: \( s_A = \frac{1}{2} \times 0.200 \times t^2 = 0.1t^2 \).
05

Solve for Time \( t \)

From \( s_G + s_A = 88 \), substitute the expressions for \( s_G \) and \( s_A \): \( 0.15t^2 + 0.1t^2 = 88 \). This simplifies to \( 0.25t^2 = 88 \). Solve for \( t^2 \): \( t^2 = \frac{88}{0.25} = 352 \). Hence, \( t = \sqrt{352} \approx 18.76 \) seconds.
06

Find Location of Collision

Substitute \( t = 18.76 \) seconds back into \( s_G = 0.15t^2 \) to find \( s_G \)'s distance. Thus, \( s_G = 0.15 \times 352 = 52.8 \) meters.

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Key Concepts

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

Acceleration
Acceleration is a key concept in physics, particularly in kinematics. It refers to the rate at which an object changes its velocity. When describing acceleration, we are interested in how quickly or slowly an object speeds up or slows down. In the context of the problem, both knights start from rest and have different accelerations.George's acceleration is given as 0.300 m/s², which tells us that for every second he rides, his velocity increases by 0.3 m/s. Similarly, Alfred's acceleration is 0.200 m/s², meaning he speeds up by 0.2 m/s each second.
  • Acceleration (\(a\)) is measured in meters per second squared (m/s²).
  • It indicates both the magnitude and the direction of velocity change.
  • An object starting from rest means its initial velocity is zero.
  • Constant acceleration results in an increase in velocity at a uniform rate.
Understanding acceleration helps us determine how far each knight travels before they collide. Since each knight accelerates differently, they cover different distances over the same period.
Relative Motion
Relative motion is the study of how different observers perceive the motion of objects. It focuses on the idea that motion is not absolute but instead depends on the frame of reference. In this problem, we consider the knights' motion relative to where Sir George starts. The concept comes into play when we calculate where the knights meet. Since they both move toward each other, the sum of their movements will cover the distance that initially separates them.
  • Relative motion involves analyzing how the positions of two or more objects change with respect to each other.
  • We fix one object as the point of reference, which simplifies calculating their relative positions.
  • In many cases, this helps solve problems by reducing the number of variables.
Here, by understanding that both knights travel towards each other, we can use their combined distance of 88 m to determine their point of collision.
Distance Calculation
Distance calculation in physics involves using formulas that relate acceleration, time, and distance. For an object accelerating from rest, the formula is:\[s = \frac{1}{2} a t^2\]where \(s\) is the distance traveled, \(a\) is the acceleration, and \(t\) is the time elapsed. Both knights in the problem use this formula to calculate the distance each travels.
  • Sir George travels a distance calculated by \(s_G = 0.15t^2\).
  • Sir Alfred's travel distance is \(s_A = 0.1t^2\).
  • Their combined traveled distance equals 88 m (\(s_G + s_A = 88\)).
After setting up the equation and solving for time, \(t\) is found to be approximately 18.76 seconds. By substituting \(t\) back into George's formula, we find he travels 52.8 meters. This shows the importance of systematic calculations and understanding the direct relationship between acceleration and distance.

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Most popular questions from this chapter

Interactive Solution \(2.31\) at offers help in modeling this problem. A car is traveling at a constant speed of \(33 \mathrm{~m} / \mathrm{s}\) on a highway. At the instant this car passes an entrance ramp, a second car enters the highway from the ramp. The second car starts from rest and has a constant acceleration. What acceleration must it maintain, so that the two cars meet for the first time at the next exit, which is \(2.5 \mathrm{~km}\) away?

A log is floating on swiftly moving water. A stone is dropped from rest from a 75 -mhigh bridge and lands on the log as it passes under the bridge. If the log moves with a constant speed of \(5.0 \mathrm{~m} / \mathrm{s}\), what is the horizontal distance between the \(\log\) and the bridge when the stone is released?

A jetliner, traveling northward, is landing with a speed of \(69 \mathrm{~m} / \mathrm{s}\). Once the jet touches down, it has \(750 \mathrm{~m}\) of runway in which to reduce its speed to \(6.1 \mathrm{~m} / \mathrm{s}\). Compute the average acceleration (magnitude and direction) of the plane during landing.

A ball is thrown upward from the top of a 25.0 -m-tall building. The ball's initial speed is \(12.0 \mathrm{~m} / \mathrm{s}\). At the same instant, a person is running on the ground at a distance of \(31.0 \mathrm{~m}\) from the building. What must be the average speed of the person if he is to catch the ball at the bottom of the building?

Multiple-Concept Example 9 reviews the concepts that are important in this problem. A drag racer, starting from rest, speeds up for \(402 \mathrm{~m}\) with an acceleration of \(+17.0 \mathrm{~m} / \mathrm{s}^{2}\). A parachute then opens, slowing the car down with an acceleration of \(-6.10 \mathrm{~m} / \mathrm{s}^{2} .\) How fast is the racer moving \(3.50 \times 10^{2} \mathrm{~m}\) after the parachute opens?

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