/*! 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 22 Find the required angular speed ... [FREE SOLUTION] | 91Ó°ÊÓ

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Find the required angular speed (in rpm) of an ultracentrifuge for the radial acceleration of a point \(2.50 \mathrm{~cm}\) from the axis to equal \(400,000 \mathrm{~g}\)

Short Answer

Expert verified
The angular speed required is approximately 47,381 rpm.

Step by step solution

01

Convert Acceleration from g to m/s²

We know that acceleration due to gravity, \( g \), is approximately \( 9.8 \text{ m/s}^2 \). Therefore, \( 400,000 \ g \) is \( 400,000 \times 9.8 \text{ m/s}^2 \). Calculate this value to convert the acceleration to m/s².
02

Convert Distance to Meters

The distance from the axis is given in centimeters and needs to be in meters for standard SI units. So, convert \( 2.50 \text{ cm} \) to meters: \( 2.50 \text{ cm} = 0.025 \text{ m} \).
03

Use Radial Acceleration Formula to Find Angular Velocity

The radial acceleration \( a \) is given by \( a = \omega^2 r \), where \( \omega \) is the angular velocity in radians per second, and \( r \) is the radius in meters. Rearrange the formula to solve for \( \omega \): \( \omega = \sqrt{\frac{a}{r}} \). Substitute \( a = 400,000 \times 9.8 \) m/s² and \( r = 0.025 \) m into the equation to find \( \omega \).
04

Convert Angular Velocity to Revolutions Per Minute (rpm)

First, convert the angular velocity from radians per second to revolutions per second by dividing by \(2\pi\), since there are \(2\pi\) radians in a revolution. Then, convert this to revolutions per minute by multiplying by 60 seconds. This gives the angular speed in rpm.

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Key Concepts

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

Centrifugal Force
Centrifugal force is often encountered when objects move in a circle. Imagine spinning around quickly while holding onto a rope attached to an object. The tendency of the object is to fly outwards away from the circle. This apparent force that pushes the object outward is what we call centrifugal force. It is often considered a "fictitious" force because it arises from the object's inertia and the circular path you are forcing it to follow.

Essentially, when an object is moving in a circular path, its inertia wants it to continue in a straight line. However, a continuous force (often called the centripetal force) keeps it in the circle. The centrifugal force is the perception of the object's desire to move straight, particularly felt by an observer within the rotating system.
  • Occurs in rotating systems.
  • Fictitious force due to inertia.
  • Always directed away from the axis of rotation.
Understanding centrifugal force is crucial when studying rotating machinery like ultracentrifuges or even when designing rides in amusement parks.
Radial Acceleration
Radial acceleration, also known as centripetal acceleration, is the acceleration that points towards the center of a circular path. It is crucial in maintaining an object's circular motion by continually changing its velocity direction.

Radial acceleration is quantified by the formula \[ a = \omega^2 r \]where - \( a \) is the radial acceleration,- \( \omega \) is the angular velocity in radians per second,- \( r \) is the radius from the center of the circle to the point object.
Given that this concept is integral to understanding circular motion, it explains why an object in a circular path needs constant force applied towards the center to keep moving in a circle. This force is necessary because the velocity direction is always changing, even if the speed is constant.
Angular Speed Calculation
Angular speed is a measure of how quickly an object is rotating. It is typically represented in radians per second or revolutions per minute (rpm). When solving problems related to rotation, angular speed is key.

To calculate angular speed, we can use radial acceleration as follows: Rearrange the radial acceleration formula,\[ a = \omega^2 r \]to find\[ \omega = \sqrt{\frac{a}{r}} \],where \( \omega \) is the angular speed and \( r \) is the radius.
  • Measure angular speed in radians/second or rpm.
  • Useful to know in systems with mechanical rotation like engines or centrifuges.
Understanding the calculation of angular speed helps in designing and operating rotating systems and ensures they function within safe limits.
SI Units Conversion
Converting measurements into the International System of Units (SI) forms the backbone of scientific calculations. Consistency in units ensures calculations are correct and comparable.

For example, when dealing with distances, it's crucial to convert units to meters, the standard SI unit for length. If you have a measurement in centimeters, you convert it by dividing by 100:\[ \text{{Centimeters}} \to \text{{Meters}} \]Similarly, accelerations given in terms of \( g \) (where \( g \approx 9.8 \text{ m/s}^2 \)) should be converted to \( \text{m/s}^2 \).
  • Standardize units to meters, kilograms, seconds.
  • Facilitates accurate and consistent calculations.
  • Aids in understanding and comparing scientific results.
Through these conversions, calculations become universally understandable and operable within the scientific community.

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Most popular questions from this chapter

BIO The Spinning Eel. American eels are freshwater fish with long, slender bodies that we can treat as a uniform cylinder \(1.0 \mathrm{~m}\) long and 10 \(\mathrm{cm}\) in diameter. An eel compensates for its small jaw and teeth by holding onto prey with its mouth and then rapidly spinning its body around its long axis to tear off a piece of flesh. Eels have been recorded to spin at up to \(14 \mathrm{rev} / \mathrm{s}\) when feeding in this way. Although this feeding method is energetically costly, it allows the eel to feed on larger prey than it otherwise could. A field researcher uses the slow-motion feature on her phone's camera to shoot a video of an eel spinning at its maximum rate. The camera records at 120 frames per second. Through what angle does the eel rotate from one frame to the next? A. \(1^{\circ}\) B. \(10^{\circ}\) C. \(22^{\circ}\) D. \(42^{\circ}\)

A car is traveling at a speed of \(101 \mathrm{~km} / \mathrm{h}\) on the highway and has a small stone stuck between the treads of one of its tires. The tires have diameter \(61.0 \mathrm{~cm}\) and are rolling without sliding or slipping. What are (a) the maximum and (b) the minimum speeds of the stone as observed by a pedestrian standing on the side of the highway?

A \(150.0 \mathrm{~kg}\) cart rides down a set of tracks on four solid steel wheels, each with radius \(20.0 \mathrm{~cm}\) and mass \(45.0 \mathrm{~kg} .\) The tracks slope downward at an angle of \(20^{\circ}\) to the horizontal. If the cart is released from rest a distance of \(16.0 \mathrm{~m}\) from the bottom of the track (measured along the slope), how fast will it be moving when it reaches the bottom? Assume that the wheels roll without slipping, and that there is no energy loss due to friction.

(a) Calculate the angular velocity (in rad/s) of the second, minute, and hour hands on a wall clock. (b) What is the period of each of these hands?

A thin uniform bar has two small balls glued to its ends. The bar is \(2.00 \mathrm{~m}\) long and has mass \(4.00 \mathrm{~kg},\) while the balls each have mass \(0.500 \mathrm{~kg}\) and can be treated as point masses. Find the moment of inertia of this combination about each of the following axes: (a) an axis perpendicular to the bar through its center; (b) an axis perpendicular to the bar through one of the balls; (c) an axis parallel to the bar through both balls.

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