Part A: In Newton\'s Law of Gravity F= GmM/R^2 How would you describe G? There m
ID: 1567178 • Letter: P
Question
Part A:
In Newton's Law of Gravity
F= GmM/R^2
How would you describe G? There may be more than one answer, so pick those that apply.
a. A constant that we can predict theoretically
b. A constant that changes from one place in the universe to another
c. A constant we can measure, but not predict. It is one of the more difficult constants to determine because gravity is so weak.
d. A constant that so far as we know is the same everywhere in space and for all time
e. A constant that is the same everywhere but changes with time
Part B:
A pontoon boat is a common sight on calm lakes and rivers. Some are as simple as sealed cylinders on each side of a deck. Suppose you have 4 barrels lashed together to make a floating "boat" or diving platform. These drums are typically 0.57 m in diameter and 0.85 meters long when designed to hold 55 gallons of liquid. The plastic ones have a mass of only 10 kg empty. What is the maximum number of average sized people who could climb onthe platform before it would sink in fresh water (density of 1 gm/cm3 or 1000 kg/m3)? A typical person would be 75 kg mass.
16
12
8
4
2
16
12
8
4
2
Explanation / Answer
(a)
A constant that we can predict theoretically is correct answer
A constant that so far as we know is the same everywhere in space and for all time is correct answer
(b)
Volume of the cylinder is
V = pi r^2 h
= pi ( 0.57/2)^2 ( 0.85)
=0.21689 m^3
volume of 4 barrels is 4 ( 0.21689) = 0.867597 m^3
weight of displaced water is W dis = 1000(0.867597 m^3)g
weight of the N people is
W = N75 kg
1000(0.867597 m^3)g = N 75 g
N = 12