/*! 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 21 In a control system, an accelero... [FREE SOLUTION] | 91Ó°ÊÓ

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In a control system, an accelerometer consists of a 4.70-g object sliding on a calibrated horizontal rail. A low-mass spring attaches the object to a flange at one end of the rail. Grease on the rail makes static friction negligible, but rapidly damps out vibrations of the sliding object. When subject to a steady acceleration of \(0.800 \mathrm{~g}\), the object should be at a location \(0.500 \mathrm{~cm}\) away from its equilibrium position. Find the force constant of the spring required for the calibration to be correct.

Short Answer

Expert verified
The force constant of the spring required for the calibration to be correct is approximately \(6.9 N/m\).

Step by step solution

01

Converting units

Convert the mass and the distance the object is displaced from the equilibrium position to kilograms and meters respectively. \n Mass: \(4.70g = 4.70 * 10^{-3} kg\) \n Displacement: \(0.500cm = 0.500 * 10^{-2} m = 0.005m\)
02

Calculating acceleration in SI units

The acceleration is given in terms of the acceleration due to gravity, represented as 'g'. Convert the acceleration to the SI unit, meters per second squared (m/s^2), by multiplying the given value by the acceleration due to gravity (approximated as 9.81 m/s^2).\n \( Acceleration = 0.8g = 0.8 * 9.81 m/s² = 7.848 m/s² \)
03

Applying Hooke's Law

Hooke's Law states that the force exerted by a spring is proportional to the displacement from the equilibrium position and can be represented as \(F_{spring} = -k * x\), where k is the spring constant, x is the displacement from the equilibrium position and F_{spring} is the force exerted by the spring. Additionally, from Newton's second law, \( F = ma \), where m is the mass and a is the acceleration. When the object is subject to a steady acceleration, the force from the spring and the gravitational force balance out, so \( F_{gravity} = F_{spring} \).\n Set the two expressions for force equal to each other and solve for k.\n \(F_{gravity} = F_{spring} \)\n \(m*a = k*x \)\n Thereby, \( k = m*a/x \)
04

Calculating the force constant

Substitute the values of m, a and x from step 1 and 2 into the formula to calculate k. \n \(k = 4.7 * 10^{-3} kg * 7.848 m/s^2 / 0.005m = 6.9N/m\)

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Key Concepts

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

Spring Constant
Hooke's Law is fundamental when working with springs and involves a parameter known as the spring constant, denoted by the symbol \( k \). The spring constant determines the stiffness of the spring. A larger \( k \) means the spring is stiffer, and a smaller \( k \) indicates a looser spring. This constant tells us how much force is needed to extend or compress the spring by a unit length. To find the spring constant in problems, use Hooke's Law equation:
  • \( F_{spring} = -k \cdot x \)
Where \( F_{spring} \) is the force exerted by the spring and \( x \) is the displacement from equilibrium.
In our exercise, we calculated \( k \) using the formula \( k = \frac{m \cdot a}{x} \), which we derived by setting the gravitational force (calculated from mass \( m \) and acceleration \( a \)) equal to the spring force.
Acceleration Conversion
Before we can apply any of the laws of motion or physics formulas correctly, converting units into a consistent system is crucial. Often in physics, acceleration is initially given relative to \( g \), the acceleration due to Earth's gravity, which equals approximately \( 9.81 \ \text{m/s}^2 \).
To convert an acceleration given in terms of \( g \) to standard SI units, multiply the given value by \( 9.81 \ \text{m/s}^2 \). For example, in the given exercise, the steady acceleration is \( 0.800 \ g \). Hence, we convert this to SI units as:
  • \( 0.800 \ g = 0.800 \times 9.81 \ \text{m/s}^2 = 7.848 \ \text{m/s}^2 \)
This conversion ensures our calculations remain accurate when applying formulas that operate in SI units.
Force Balance
In mechanical systems, understanding force balance is vital to predicting the motion of an object. Force balance occurs when the net force acting on an object is zero, resulting in a steady state or constant velocity. In our accelerometer setup, achieving a correct calibration requires balancing the force that results from the spring with the effective force arising from acceleration and mass.
  • Newton's Second Law states: \( F = m \cdot a \)
  • Hooke's Law for spring force is: \( F_{spring} = k \cdot x \)
For the system in equilibrium during acceleration, we equate the force of the spring to the force due to acceleration:
  • \( m \cdot a = k \cdot x \)
This equation allows us to solve for the spring constant \( k \), crucial for designing systems such as accelerometers where precise measurement of displacement in response to acceleration is needed.

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Most popular questions from this chapter

BIO In bicycling for aerobic exercise, a woman wants her heart rate to be between 136 and 166 beats per minute. Assume that her heart rate is directly proportional to her mechanical power output. Ignore all forces on the woman- plus-bicycle system, except for static friction forward on the drive wheel of the bicycle and an air resistance force proportional to the square of the bicycler's speed. When her speed is \(22.0 \mathrm{~km} / \mathrm{h}\), her heart rate is \(90.0\) beats per minute. In what range should her speed be so that her heart rate will be in the range she wants?

QiC A shopper in a supermarket pushes a cart with a force of \(35 \mathrm{~N}\) directed at an angle of \(25^{\circ}\) below the horizontal. The force is just sufficient to overcome various frictional forces, so the cart moves at constant speed. (a) Find the work done by the shopper as she moves down a \(50.0-\mathrm{m}\) length aisle. (b) What is the net work done on the cart? Why? (c) The shopper goes down the next aisle, pushing horizontally and maintaining the same speed as before. If the work done by frictional forces doesn't change, would the shopper's applied force be larger, smaller, or the same? What about the work done on the cart by the shopper?

A \(7.00-\mathrm{kg}\) bowling ball moves at \(3.00 \mathrm{~m} / \mathrm{s}\). How fast must a 2.45-g Ping-Pong ball move so that the two balls have the same kinetic energy?

A daredevil wishes to bungee-jump from a hot-air balloon \(65.0 \mathrm{~m}\) above a carnival midway. He will use a piece of uniform elastic cord tied to a harness around his body to stop his fall at a point \(10.0 \mathrm{~m}\) above the ground. Model his body as a particle and the cord as having negligible mass and a tension force described by Hooke's force law. In a preliminary test, hanging at rest from a \(5.00-\mathrm{m}\) length of the cord, the jumper finds that his body weight stretches it by \(1.50 \mathrm{~m}\). He will drop from rest at the point where the top end of a longer section of the cord is attached to the stationary balloon. (a) What length of cord should he use? (b) What maximum acceleration will he experience?

\(\mathrm{S}\) A projectile of mass \(m\) is fired horizontally with an initial speed of \(v_{0}\) from a height of \(h\) above a flat, desert surface. Neglecting air friction, at the instant before the projectile hits the ground, find the following in terms of \(m, v_{0}, h\), and \(g\) : (a) the work done by the force of gravity on the projectile, (b) the change in kinetic energy of the projectile since it was fired, and (c) the final kinetic energy of the projectile. (d) Are any of the answers changed if the initial angle is changed?

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