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Gravity Lab Introduction KEY
Name Score:____/
1. Go to http://phet.colorado.edu/en/simulation/gravity-force-lab
2. Select RUN
Qualitative Observations (7 points)
- Move the masses closer. When they move closer the force between them becomes
_________________________ (Greater/Less/the same)
- Move the masses further apart. When the masses move away the force between them becomes
_________________________ (Greater/Less/the same)
- Double Mass 1. When mass 1 is doubled the force between them becomes
_________________________ (Greater/Less/the same)
- Cut Mass 2 in half. When the mass is reduced the force between them becomes
_________________________ (Greater/Less/the same)
- In any of the situations did the forces ever differ in magnitude?
No. the forces always have the same magnitude, but the opposite direction
- In any of the situations did the forces ever not point in opposing directions?
No. they always point in the opposite direction
- What physics LAW explains questions 5 and 6 (either give name or definition)
Newton’s Third Law – action-reaction forces
Quantitative Observations
MASS
It is now time to build a model. First, let us examine the relationship between masses.
a) Separate Mass 1 and Mass 2 so that their centers of mass (black dots) are 6 meters apart.
b) Set Mass 2 to 30.0 kg.
c) Start Mass 1 at zero kg. Collect 10 data points with the gravitational force being your dependent variable
and your Mass 1 being an independent variable. Create a data table in the space below. (5 points)
Force of gravity (N) M1 (kg) M2 (kg) 0 0 30 5.5 0 x10-^10 10 1.10 x 10-^9 20
- 6 6x 10-^9 30 2.21 x 10-^9 40 2.76 x 10-^9 50 3.31 x 10-^9 60 3.87 x 10-^9 70 4.42 x 10-^9 80 4.97 x 10-^9 90 5.52 x 10-^9 100
d) Sketch a graph Force of Gravity vs. Mass 1 either by hand or by using MS Excel. (5 points)
Mass 1 (kg)
Fg (N)
DISTANCE
a) Set both masses to 30.0 kg.
b) Collect 10 data points of different distances between the masses. Hint: you can move the ruler and the masses to maximize your range.
Create a data table in the space below. (5 points)
c) Sketch a graph of Force of Gravity vs. Distance (F vs. r) by hand or by using MS Excel. (5 points)
10. What is the relationship between distance and the force of gravity? (2 points)
There are inversely proportional to each other. When one of the quantities increases, the other one decreases; if one of them decreases, the other one increases as well. It’s an inverse relationship (inverse power law).
Force of gravity (N) Distance (m) M 2 (kg) M 1 (kg) 6.00 x10-^10 10 30 7.40 x 10-^10 9 30 9.40 x 10-^10 8 30
- 22 x 10-^9 7 30 1.66 x 10-^9 6 30
- 41 x 10-^9 5 30
- 77 x 10-^9 4 30
- 63 x 10-^9 3 30 5.16 x 10-^9 3.4 30 30 8.83 x 10-^9 2.6 30 30
Distance (m)
Fg (N)
d) Linearize the graph. Create a data table in the space below and sketch it using MS Excel or by hand. Be
- Force of Gravity vs Distance-1 Force of Gravity vs Distance- careful! (5 points) - Force of Gravity vs Distance-
- 6.00 x10-^10 10 0.100 0.0100 0. Force of gravity (N) Distance (m) Distance-^1 (m-^1 ) Distance-^2 (m-^2 ) Distance-^3 (m-^3 )
- 7.40 x 10-^10 9 0.110 0.0123 0.
- 9.40 x 10-^10 8 0.125 0.0156 0. - 1. 22 x 10 -^9 7 0.143 0.0204 0. - 1.66 x 10-^9 6 0.167 0.0278 0. - 2. 41 x 10-^9 5 0.200 0.0400 0. - 3. 77 x 10-^9 4 0.250 0.0625 0. - 6 63 x 10-^9 3 0.333 0.1111 0. - 5.16 x 10-^9 3.4 0.294 0.0865 0. - 8.83 x 10-^9 2.6 0.385 0.148 0.
Force of Gravity vs Proportionality (m1 · m2/r^2 )
Determine the gravitational constant (G) that will multiply to your units. Give the gravitational constant proper unit too. SHOW all your work below.
Hint: all your units combined need to = a Newton. (5 points)
Calculate slope. That will be G!
G = slope = (8 x 10-9^ N) – (4 x 10-9^ N) = 6.666666 x 10-11= 120 kg^2 ·m-2^ – 60 kg^2 ·m-
G = 6.67 x 10
N·m
/kg
Write your full formula and check with Mr. Vlacil. Congratulations!
Fg = 6.67 x 10
- 11 m1 · m
r
2
