Lab Assignment 9: Gravity
Instructor’s Overview
As you continue with your study of physics, you’ll learn that there are four fundamental interactions in nature. These interactions are summarized in this table:
Interaction |
Comments |
Relative strength |
Effective range |
Strong nuclear force |
Binds protons and neutrons in nuclei |
1 |
10-15 m
|
Electromagnetic force |
Force between charged particles. Follows inverse- square law. |
10-2 |
Infinite |
Weak force |
Responsible for certain types of radioactive decay |
10-13
|
10-18 m |
Gravitational force |
Force between all objects. Determined by magnitude of masses and separation. Follows inverse-square law. |
10-38
|
Infinite |
So gravity is one of the four fundamental forces of nature. We will learn about the other three in Physics II. Some interesting things to note about the gravitational force:
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1 Physics I
Experiment 1: In the first part of the lab, you will subject a variety of objects to the force of gravity and discuss your observations.
Experiment 2: In the second part of the lab, you will use a flashlight as an analogy to demonstrate the inverse-square law of gravity.
Take detailed notes as you perform the experiment and fill out the sections below. This document serves as your lab report. Please include detailed descriptions of your experimental methods and observations.
Date:
Student: Abstract
Introduction
Material and Methods
Results
Based on your results from the experiments, please answer the following questions:
Experiment 1: Falling in a Gravitational Field
1. The following expression for the acceleration due to gravity works well for objects near the Earth’s surface (G is the gravitational constant, Me is the mass of the Earth, and Re is the radius of the Earth):
=
2
Use the above equation to calculate the gravitational acceleration at an altitude of 100,000 meters above the Earth. By what percentage is this acceleration different from that on the Earth’s surface?
2. How does air resistance alter the way we perceive falling objects?
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2 Physics I
3. Using the universal law of gravitation, show that the gravitational acceleration experienced by an object is independent of its mass.
Experiment 2: Inverse Square Law Data table
Distance from wall |
Diameter of light circle |
Radius of light circle |
Area of light circle |
NOTE: Be sure to specify your units.
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6. If you moved too far away from the wall the circle of light probably became very difficult to see. Is the intensity of the light circle ever zero? Is it correct to say that gravity doesn’t exist between objects on opposite sides of the galaxy?
Conclusions
References
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