/*! 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 68 An \(x\) -ray tube accelerates e... [FREE SOLUTION] | 91Ó°ÊÓ

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An \(x\) -ray tube accelerates electrons from rest at \(5 \times 10^{14} \mathrm{~m} / \mathrm{s}^{2}\) through a distance of \(15 \mathrm{~cm}\). Find (a) the electrons' velocity after this acceleration and (b) the acceleration time. (Such high accelerations are possible because electrons are extremely light.)

Short Answer

Expert verified
Electron's final velocity is approximately \( 1.225 \times 10^7 \, \text{m/s} \) and acceleration time is approximately \( 2.45 \times 10^{-8} \, \text{s} \).

Step by step solution

01

Identify Known Quantities and Formulas

We know that the initial velocity of the electrons, \( u = 0 \), the acceleration \( a = 5 \times 10^{14} \, \text{m/s}^2 \), and the distance \( s = 15 \, \text{cm} = 0.15 \, \text{m} \). We will use the kinematic equations to find velocity and time.
02

Calculate Final Velocity

Using the kinematic equation \( v^2 = u^2 + 2as \), plug the known values: \( v^2 = 0 + 2(5 \times 10^{14})(0.15) \). Simplify to get \( v^2 = 1.5 \times 10^{14} \). Taking the square root, we find \( v = \sqrt{1.5 \times 10^{14}} \).
03

Solve for the Final Velocity

Calculating the square root, we get \( v \approx 1.225 \times 10^7 \, \text{m/s} \). Thus, the final velocity of the electrons is approximately \( 1.225 \times 10^7 \, \text{m/s} \).
04

Calculate Acceleration Time

Use the kinematic equation \( v = u + at \). Substituting the known values gives us \( 1.225 \times 10^7 = 0 + (5 \times 10^{14})t \). Simplify to solve for \( t \): \( t = \frac{1.225 \times 10^7}{5 \times 10^{14}} \).
05

Solve for the Acceleration Time

After calculating, \( t \approx 2.45 \times 10^{-8} \, \text{s} \). Hence, the acceleration time is approximately \( 2.45 \times 10^{-8} \, \text{s} \).

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Key Concepts

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

Understanding Acceleration
Acceleration is a key concept in kinematics, which is the study of motion. It describes how quickly the velocity of an object changes over time. Imagine pressing the accelerator in a car; the harder you press, the quicker the car speeds up. Similarly, acceleration in physics tells us how fast an object's speed or velocity is changing.
In our exercise, the electrons experience an acceleration of \(5 \times 10^{14} \, \text{m/s}^2\). This means their velocity increases by this amount every second during the acceleration phase. This incredibly high rate is achievable due to the electrons' tiny mass, allowing them to reach high velocities quickly.
  • Initial Velocity \( u \): Prior to acceleration, the velocity of the electrons is zero, as they start from rest.
  • Acceleration \( a \): Provided as \(5 \times 10^{14} \, \text{m/s}^2\) in the problem.
Understanding these parameters helps us predict how the electrons will behave under force.
Finding Final Velocity
Final Velocity represents the speed an object achieves after a period of acceleration. It's like when a car reaches a certain speed after accelerating from a stop.
To calculate this for the electrons, we use one of the kinematic equations: \[ v^2 = u^2 + 2as \] Here, \( v \) is the final velocity, \( u \) is the initial velocity (\(0\) in our scenario), \( a \) is acceleration, and \( s \) is the distance traveled. Plugging in the values, \[ v^2 = 0 + 2(5 \times 10^{14})(0.15) \] Solving gives us \( v^2 = 1.5 \times 10^{14} \). Taking the square root, we find \[ v = \sqrt{1.5 \times 10^{14}} \approx 1.225 \times 10^7 \, \text{m/s} \] This impressive velocity indicates how swiftly the electrons are moving after acceleration.
Introduction to Kinematic Equations
Kinematic equations are powerful tools in physics to solve problems involving motion. They link several motion variables: initial velocity, final velocity, acceleration, time, and displacement.
  • One such equation used in our problem is \( v^2 = u^2 + 2as \).
  • Another equation employed is \( v = u + at \), where \( t \) is the time of acceleration.
These equations allow you to solve for unknown variables when you have sufficient known values. For example, in our exercise, we used them to find how fast the electrons moved and how long it took. By understanding these relationships, you can predict various aspects of motion easily. It's like having a recipe that tells you what ingredients you need and how long to cook.

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Most popular questions from this chapter

A rocket accelerates straight up from the ground at \(12.6 \mathrm{~m} / \mathrm{s}^{2}\) for \(11.0 \mathrm{~s}\). Then the engine cuts off and the rocket enters free fall. (a) Find its velocity at the end of its upward acceleration. (b) What maximum height does it reach? (c) With what velocity does it crash to Earth? (d) What's the total time from launch to crash?

You're approaching an intersection at \(50 \mathrm{~km} / \mathrm{h}(13.9 \mathrm{~m} / \mathrm{s})\) You see the light turn yellow when you're \(35 \mathrm{~m}\) from the intersection. Assume a reaction time of 0.6 s before braking begins and a braking acceleration of \(-3.0 \mathrm{~m} / \mathrm{s}^{2}\). (a) Will you be able to stop before the intersection? (b) The yellow light stays on for \(3.4 \mathrm{~s}\) before turning red. If you continue at \(50 \mathrm{~km} / \mathrm{h}\) without braking, will you make it through the \(9.5-\mathrm{m}\) -wide intersection before the light turns red?

An object is dropped from rest off the \(442-\mathrm{m}\) Sears Tower in Chicago. Its fall time is (a) \(45.1 \mathrm{~s} ;\) (b) \(19.1 \mathrm{~s} ;\) (c) \(9.5 \mathrm{~s} ;\) (d) \(4.7 \mathrm{~s}\).

The next three problems deal with a stock car, which starts from rest at time \(t=0\) with velocity \((\mathrm{m} / \mathrm{s})\) increasing for \(4.0 \mathrm{~s}\), according to the function \(v_{x}=1.4 t^{2}+1.1 t\) Estimate the instantaneous acceleration at \(t=2.0 \mathrm{~s}\).

A runner is planning for a \(10-\mathrm{km}\) race. She can maintain a steady speed of \(4.10 \mathrm{~m} / \mathrm{s}\) for as much time as needed before ending the race with a \(7.80-\mathrm{m} / \mathrm{s}\) sprint. If she wants to finish in 40 min or less, how far from the finish should she begin to sprint?

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