Chapter 2: Problem 52
A bolt is dropped from a bridge under construction, falling \(90 \mathrm{~m}\) to the valley below the bridge. (a) In how much time does it pass through the last \(20 \%\) of its fall? What is its speed (b) when it begins that last \(20 \%\) of its fall and \((\mathrm{c})\) when it reaches the valley beneath the bridge?
Short Answer
Step by step solution
Analyze the Problem
Calculate Total Fall Time
Determine Last 20% of Fall Distance
Calculate Time to Reach Last 20%
Calculate Time for Last 20% of Fall
Speed at Beginning of Last 20%
Speed Upon Reaching the Valley
Unlock Step-by-Step Solutions & Ace Your Exams!
-
Full Textbook Solutions
Get detailed explanations and key concepts
-
Unlimited Al creation
Al flashcards, explanations, exams and more...
-
Ads-free access
To over 500 millions flashcards
-
Money-back guarantee
We refund you if you fail your exam.
Over 30 million students worldwide already upgrade their learning with 91Ó°ÊÓ!
Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Velocity Calculations
In free fall, the velocity can be calculated using the formula: \( v = g \times t \), where \( v \) stands for velocity, \( g \) is the acceleration due to gravity, and \( t \) is the time. This formula shows that velocity increases linearly over time while falling under gravity alone.
- During the initial seconds of free fall, the speed is relatively low.
- As time progresses, the speed continues to increase at a steady rate determined by gravity.
Acceleration Due to Gravity
To grasp how acceleration due to gravity functions, consider:
- Each second a free-fall object drops, it's gaining around 9.8 meters per second in speed.
- This means if you start at 0 m/s, after 1 second, you are moving at 9.8 m/s; after 2 seconds, at approximately 19.6 m/s, and so on.
Distance-Time Relationship
The formula \( s = \frac{1}{2} g t^2 \) encapsulates this relationship, where \( s \) is the distance fallen, \( g \) is gravitational acceleration, and \( t \) is time. The equation reflects how the distance increases quadratically with time, highlighting that the longer an object falls, the faster it accumulates distance.
- Initially, the object covers a small distance in the first few seconds.
- As the fall continues, the distance covered grows rapidly due to the square of time in the equation.
- For example, doubling the time doesn't just double the distance—it quadruples it.
Projectile Motion
In the specific case of a free-falling object like a bolt dropped vertically with no initial horizontal velocity, the interesting part is the vertical motion driven solely by gravity.
- The only force here is gravity, pulling the object downward.
- Despite the absence of initial horizontal motion, the principles of projectile motion still apply in analysis.
- Vertical component analysis allows for precise calculation of how fast an object will be moving at any point in time.