/*! 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 115 A stalactite on the roof of a ca... [FREE SOLUTION] | 91Ó°ÊÓ

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A stalactite on the roof of a cave drips water at a steady rate to a pool \(4.0 \mathrm{m}\) below. As one drop of water hits the pool, a second drop is in the air, and a third is just detaching from the stalactite. (a) What are the position and velocity of the second drop when the first drop hits the pool? (b) How many drops per minute fall into the pool?

Short Answer

Expert verified
(a) Position: 1.0 m, Velocity: 4.43 m/s; (b) Drops per minute: 66.44.

Step by step solution

01

Understanding the Problem

To solve this problem, we need to determine the position and velocity of the second drop when the first drop hits the pool, and also how frequently these drops fall. We'll apply the concepts of free fall motion under uniform gravity (ignoring air resistance) to solve this.
02

Calculate Time for First Drop to Fall

We use the equation of motion: \[ h = \frac{1}{2} g t^2 \]Where \( h = 4.0 \, \text{m} \) and \( g = 9.8 \, \text{m/s}^2 \). Solving for \( t \),\[ 4.0 = \frac{1}{2} \cdot 9.8 \cdot t^2 \]\[ t^2 = \frac{4.0 \times 2}{9.8} \]\[ t = \sqrt{\frac{8.0}{9.8}} \approx 0.903 \, \text{s} \]This is the time it takes for the first drop to reach the pool.
03

Determine Position and Velocity of Second Drop

When the first drop hits the pool at \( t = 0.903 \, \text{s} \), the second drop has been falling for half this time (since at the start, the first and second drop are separated by the time it takes one drop to fall). Thus, \( t = \frac{0.903}{2} \approx 0.4515 \, \text{s} \).Position using \( y = \frac{1}{2}gt^2 \):\[ y = \frac{1}{2} \cdot 9.8 \cdot (0.4515)^2 \approx 1.0 \, \text{m} \]Velocity using \( v = gt \):\[ v = 9.8 \cdot 0.4515 \approx 4.43 \, \text{m/s} \]
04

Calculate Frequency of Drops Hitting the Pool

To find how often drops hit the pool, consider the time for the first drop to complete its fall is the interval between successive hits. From Step 2, this time is \( 0.903 \, \text{s} \). Thus, drops fall every \( 0.903 \, \text{s} \).The number of drops per minute is:\[ \frac{60 \, \text{s/min}}{0.903 \, \text{s/drop}} \approx 66.44 \, \text{drops/min} \]

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Key Concepts

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

Understanding Uniform Gravity
When we talk about uniform gravity, we are referring to a scenario where the gravitational force acting on an object is constant, such as near the surface of the Earth. In physics, this simplifies calculations because the gravitational acceleration, usually denoted as \( g \), remains a steady \( 9.8 \, \text{m/s}^2 \). This constant acceleration means that, in the absence of air resistance, all objects in free fall will experience the same gravitational pull.

In the context of the exercise, we assume uniform gravity to calculate the position and velocity of falling water drops from the stalactite. Ignoring air resistance enables us to use simple equations of motion to predict the drop's behavior. Understanding that gravity is uniform allows us to calculate that the acceleration acting on each drop remains unchanged as they fall, simplifying our mathematical approach.
Exploring Equations of Motion
The equations of motion are essential tools in mechanics, governing how objects move under certain forces. In the case of free fall, they help us understand not just distance covered but also velocity attained over time.
  • The basic equation \( h = \frac{1}{2} g t^2 \) allows us to calculate the distance \( h \) an object falls over time \( t \), given constant acceleration \( g \).
  • Another fundamental equation is \( v = gt \), which calculates the object's velocity \( v \) at any given time \( t \) during free fall.
By applying these equations, as seen in the solution steps provided in the exercise, we derived that the time for the first water drop to fall 4 meters is approximately 0.903 seconds. Likewise, the position and velocity of the second drop when the first hits the pool are determined using these same principles. These calculations showcase the power of equations of motion to predict both position and velocity accurately based on time and constant gravitational acceleration.
Calculating Position and Velocity
Understanding how to calculate position and velocity in free fall is crucial for solving many physics problems. By applying free fall mechanics, we can determine both how far and how fast an object is traveling at any point during its descent.

In the original exercise, we focused on the second drop. By knowing it starts its fall as the first completes half its journey, we know it's been falling for approximately 0.4515 seconds when the first hits the pool. Using the formula for position \( y = \frac{1}{2}gt^2 \), we predicted that it falls about 1 meter by this time.
  • To find the velocity, we applied the basic formula \( v = gt \), resulting in a velocity of nearly 4.43 meters per second.
These calculations illuminate how each drop moves through the air, linking the key aspects of vertical motion through simple yet precise equations. By mastering these calculations, students can better understand and predict the motion of any freely falling object under uniform gravitational conditions.

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Most popular questions from this chapter

A finch rides on the back of a Galapagos tortoise, which walks at the stately pace of \(0.060 \mathrm{m} / \mathrm{s}\). After \(1.2 \mathrm{minutes}\) the finch tires of the tortoise"s slow pace, and takes flight in the same direction for another 1.2 minutes at \(12 \mathrm{m} / \mathrm{s}\). What was the average speed of the finch for this 2.4 -minute interval?

You drive your car in a straight line at \(15 \mathrm{m} / \mathrm{s}\) for \(10 \mathrm{kilometers},\) then at \(25 \mathrm{m} / \mathrm{s}\) for another \(10 \mathrm{kilome}^{-}\) ters. (a) Is your average speed for the entire trip more than, less than, or equal to \(20 \mathrm{m} / \mathrm{s} ?\) (b) Choose the best explanation from among the following: I. More time is spent at \(15 \mathrm{m} / \mathrm{s}\) than at \(25 \mathrm{m} / \mathrm{s}\). II. The average of \(15 \mathrm{m} / \mathrm{s}\) and \(25 \mathrm{m} / \mathrm{s}\) is \(20 \mathrm{m} / \mathrm{s}\) III. Less time is spent at \(15 \mathrm{m} / \mathrm{s}\) than at \(25 \mathrm{m} / \mathrm{s}\).

Wrongly called for a foul, an angry basketball player throws the ball straight down to the floor. If the ball bounces straight up and returns to the floor \(2.8 \mathrm{s}\) after first striking it, what was the ball's greatest height above the floor?

As a train accelerates away from a station, it reaches a specd of \(4.7 \mathrm{m} / \mathrm{s}\) in \(5.0 \mathrm{s}\). If the train's acceleration remains constant. what is its speed after an additional 6.0 s has elapsed?

You drop a ski glove from a height \(h\) onto fresh snow, and it sinks to a depth \(d\) before coming to rest. (a) In terms of \(g\) and \(h,\) what is the speed of the glove when it reaches the snow? (b) What are the magnitude and direction of the glove's acceleration as it moves through the snow, assuming it to be constant? Give your answer in terms of \(g, h,\) and \(d\).

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