Virtual Activity: Universal Gravitation
Name: _______________________
PhET: Universal Law of Gravitation
Part I. Set the simulation to scientific notation to make reading the numbers easier. Manipulate the simulation to see the effect that
changing one mass has on the force between them.
Using the formulas below, imagine that mass 2 is orbiting mass 1. You will need to calculate the speed out to 5 or 6 decimal places to
see the changes.
Key formulas:
2π𝑟
𝑣 = 𝑇 where T is the period of revolution (amount of time for one revolution)
2
𝐹𝑐 = 𝑚
𝑣
𝑟
Trial
Mass 1
(kg)
Mass 2
(kg)
Radius
between
objects
Force
Speed
Period
1
1000
50
Constant
.0000002
08565
1.2917x10^-4
194569
2
1000
100
Constant
.0000004
17130
1.29171x10^-4
194569
3
1000
150
Constant
.0000006
25695
1.2917120x10^4
194569
4
1000
200
Constant
.0000008
34260
5
1000
250
Constant
.0000010
42825
6
1000
300
Constant
.0000012
51390
1.2917120422x
10^-4
1.291712x10^-4
1.2917120422x
10^-4
194569
194569
194569
How is gravitational force related to mass? Justify your answer using a graph. You can graph in Google sheets and insert your graph
here or do it by hand.
X=mass
y=gravitational force
What if the mass of body 2 was increased? How would this affect the orbit and how would it affect body 1? Use Newton’s 2nd and
3rd Laws to justify your answer.
The speed increases but the period stay the same. Newtons second law states that more mass would also
mean more force as long as acceleration is constant. Newtons third law idk
Part II. Repeat the process, this time holding the mass of both bodies constant and varying radius.
Mass 1
Mass 2
Radius
between
objects
Force
1
100
10
1
.000000066
741
2
100
10
2
.000000016
685
Trial
3
100
10
3
.000000007
416
4
100
10
4
.000000004
171
5
100
10
5
.000000002
670
6
100
10
6
.000000001
854
Speed
Period
8.1695x10^5
76910.1
5.7766x10^5
217536
4.71677x10^
-5
399628
4.0846x10^5
615304
3.6537x10^5
859823
3.335266x10
^-5
1130317.9
How is gravitational force related to radius? Justify your answer using a graph. Linearize your data, if necessary. You can graph in
Google sheets and insert your graph here or do it by hand.
Gravitational force is inversely proportional to the square of the radius
Part III.
1. Do both masses matter?
no
2. Which is the bigger driver for gravitational force: mass or radius? Justify your answer.
I think that mass is more important because it is directly correlated in a linear relationship while the radius is inversely related to
the square of the radius