/*! 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 44 A small lead ball, attached to a... [FREE SOLUTION] | 91Ó°ÊÓ

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A small lead ball, attached to a 1.5-m rope, is being whirled in a circle that lies in the vertical plane. The ball is whirled at a constant rate of three revolutions per second and is released on the upward part of the circular motion when it is 0.75 m above the ground. The ball travels straight upward. In the absence of air resistance, to what maximum height above the ground does the ball rise?

Short Answer

Expert verified
The ball rises to a maximum height of approximately 41.37 meters above the ground.

Step by step solution

01

Determine Initial Velocity

First, calculate the initial linear velocity of the ball when it is released. The ball is making three revolutions per second. The circumference of the circle is \(2 \pi r = 2 \pi (1.5) = 3\pi\) meters. Therefore, the initial velocity \(v_i\) is \(3 \times 3\pi = 9\pi\) meters per second.
02

Identify Initial Height and Energy Conservation

The ball is released at a height of 0.75 meters above the ground. To find the maximum height the ball reaches, use the principle of conservation of mechanical energy. The equation is \(\text{Total Initial Energy} = \text{Total Final Energy}\). Calculate using kinetic energy \(\text{KE}_i\) and gravitational potential energy \(\text{PE}_i\): \[ \frac{1}{2}mv_i^2 + mgh_i = mgh_f \] where \(h_f\) is the final height.
03

Solve for Maximum Height

Substitute the known values into the energy conservation equation: \[ \frac{1}{2}(9\pi)^2 + 9.8 \times 0.75 = 9.8h_f \]. To find \(h_f\), calculate: \[ \frac{1}{2}(81\pi^2) + 7.35 = 9.8h_f \]. Simplify and solve for \(h_f\) : \[ 0.5 \times 81 \times \pi^2 + 7.35 = 9.8h_f \]. Thus, \(h_f \) can be calculated to be approximately 41.37 meters.

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Key Concepts

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

Mechanical Energy Conservation
In physics, the principle of mechanical energy conservation is a crucial concept that states the total mechanical energy in a system remains constant, as long as there are no non-conservative forces, like friction, acting on it. This means that the sum of kinetic energy (energy of motion) and potential energy (stored energy) remains the same.
For the lead ball in our problem, we assume no air resistance. Thus, energy conservation is applicable. At the point of release, the ball's mechanical energy is a mix of kinetic energy due to its speed and potential energy from its height. As it moves upward, kinetic energy converts to potential energy. At its highest point, all energy is potential.
This highlights a vital aspect of energy conservation: kinetic and potential energy can transform into each other, but their sum remains unchanged under conservative forces. This transforms often complex physical notions into simpler calculations.
Kinematics
Kinematics helps describe the motion of objects without considering the forces causing the motion. It's about understanding parameters like velocity, acceleration, displacement, and time. In this situation, we focus on the velocity of the ball and its subsequent motion after release.
Initially, kinematics principles guide us in determining the ball's velocity upon release. Using the distance it covers each second (taken from its circular motion parameters) gives insights into its linear velocity—a key factor in knowing how high it will reach.
Understanding velocity's role in converting kinetic to potential energy is also essential to evaluate how these energies are altered through the ball's course.
Circular Motion
Circular motion, especially uniform circular motion, describes an object's movement along the circumference of a circle at a constant speed. Here, the ball attached to the rope is initially in circular motion, spinning three times each second around the 1.5-meter radius of its path.
The connection between circular motion and linear motion is highlighted through the ball's velocity. The circumference tells us the extent of each revolution, and by recognizing the revolutions per second, we ascertain the initial speed.
An important takeaway from circular motion in this exercise is the understanding of how it gives rise to linear motion when released, essentially translating the rotational energy into linear kinetic energy.
Initial Velocity Calculation
The calculation of initial velocity can often be the first step in solving many motion-related problems. In this context, we need to calculate how fast the ball was moving when it was released from its circular path.
Given the ball completes three revolutions per second, we determine one revolution's distance using the circle's circumference formula: \( 2\pi r \). Here, \( r = 1.5 \) meters. Therefore, each revolution covers \( 3\pi \) meters, and with three revolutions per second, the ball’s initial velocity is \( 9\pi \) meters per second.
Accurately identifying this initial velocity is pivotal for further calculations like determining the ball's maximum height. It forms the basis for all subsequent energy transformations as the ball travels upwards converting kinetic energy into potential energy until reaching its peak height.

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Most popular questions from this chapter

A pendulum consists of a small object hanging from the ceiling at the end of a string of negligible mass. The string has a length of 0.75 m. With the string hanging vertically, the object is given an initial velocity of 2.0 m/s parallel to the ground and swings upward on a circular arc. Eventually, the object comes to a momentary halt at a point where the string makes an angle \(\theta\) with its initial vertical orientation and then swings back downward. Find the angle \(\theta\) .

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