IB A5.3-Gravity and Orbit
Get the Formative Assessment: FA05.3.docx
The Assessment Solved:
1. What is the force of gravity between the Philae probe with a mass of 100. kg and comet 67P with a mass of 1.05x1013 kg if the probe is resting on the surface of the 2.05 km radius comet. (That we will pretend is spherical - it's highly not)
( 0.0167 N )
2. What distance needs to separate the centers of two 5.20 kg spheres so that the force of gravity between them is 1.20x10-9 N
(1.23 m )
If you need more practice doing simple gravity problems, see the section below where I have videos for gravity whiteboards:
3. Your 12,500 kg spaceship is orbiting 1.16x107 m from the center of a planet every 17,500 s. What is the mass of the planet?
(3.02x1024 kg)
4. At what distance from the center of our 7.35x1022 kg moon is the orbital velocity 340. m/s?
(4.24x107 m)
5. Draw the new orbit: (Circle or oval indicates your current orbit)
(Watch the video to grade your FA - Strongly suggest you scroll down to the bottom and watch the "Orbital Trajectory Videos" in the table)
Slow at x: Speed up at x: Speed up at x:
(elliptical, inside, tangent at x) (more elliptical, outside orbit, tangent at x) (less elliptical, outside orbit, tangent at x)
Orbit Problems: (Links are video solutions)
1. What is the orbital velocity 3400 m from the center of a 5.6 x 1018 kg asteroid? (331.4 ≈ 330 m/s) VCO#7
2. You find that you can orbit at 516 m/s 12,150 m from the center of a small moon. What is its mass? (4.85 x 1019 kg) VCO#8
3. What distance from the center of the moon is your orbital velocity 120 m/s? (3.4 x 108 m) VCO#9
4. A satellite orbits a planet at a distance of 7.5 x 106 m from the center every 8900 seconds. What is the mass of the planet? (3.2 x 1024 kg) VCO#10
5. What is the period of orbit of a satellite that orbits 1.95 x 106 m from the center of the moon? (7730 s) VCO#11
6. What is the radius of an orbit with a period of 3.16 x 107 s around the sun? (1.50 x 1011 m – yep – it’s the earth) VCO#12
More Practice Problems:
Orbit and Gravity Questions from A5.3
Use the value of G = 6.67x10-11 Nm2/kg21. a. What is the force of gravity between a 6.50x1016 kg asteroid and a 18,700 kg spaceship if their centers are 1,450 m distant? 1:54 Practice 5 3 #1a
b. The centers of two lead spheres are separated by 6.70 m. If one sphere has a mass of 56.0 kg, and there is an attractive force of 3.70x10-9 N, what is the mass of the other sphere? 1:44 Practice 5 3 #1b
c. You are orbiting the planet Qwrmczl at a radius of 1.45x107 m, at a velocity of 3410 m/s. What is its mass?5:23 Practice 5 3 #1c
d. What is the period of an orbit that is 3.90x108 m from earth's center? (m = 5.97x1024 kg) 2:53 Practice 5 3 #1d
2. a. What is the force of gravity between a 2.60x1013 kg asteroid and a 56,100 kg spaceship if their centers are 3,560 m distant? 1:36 Practice 5 3 #2a
b. What distance separates the centers of two lead spheres if one has a mass of 123 kg, the other a mass of 12.0 kg and there is an attractive force of 3.20x10-12 N? 1:42 Practice 5 3 #2b
c. You are orbiting the planet Wnnydrydrl at a radius of 7.80x106 m, and a period of 2.30x104 seconds. What is the planet’s mass? 3:31 Practice 5 3 #2c
d. What is the radius of an orbit around earth (m = 5.97x1024 kg) that has an orbital velocity of 27.2 m/s? 1:32 Practice 5 3 #2d
3. a. What is the force of gravity between a 2.10x1015 kg asteroid and a 23,800 kg spaceship if their centers are 915 m distant? <Video>
b. The centers of two lead spheres are separated by 1.35 m. If one sphere has a mass of 125 kg, and there is an attractive force of 1.30x10-8 N, what is the mass of the other sphere? <Video>
c. What is the radius of the orbit that has an orbital velocity of 1260 m/s around the earth? (m = 5.97x1024 kg) <Video>
d. What is the period of an orbit with a radius of 3.10x107 m around the moon? (Moon’s mass is 7.36x1022 kg) <Video>
4. a. What is the force of gravity between a 2.30x1014 kg asteroid and a 12,700 kg spaceship if their centers are 1,640 m distant?
b. What distance separates the centers of two lead spheres if one has a mass of 215 kg, the other a mass of 125 kg and there is an attractive force of 6.40x10-7 N?
c. What is the period of the orbit that has a radius of 9.50x107 m around the earth? (m = 5.97x1024 kg)
d. You orbit the planet Kssnndnnwrr at a radius of 8.20x107 m with a velocity of 7830 m/s. What is its mass?
5. a. What is the force of gravity between a 23.6x1012 kg asteroid and a 14,600 kg spaceship if their centers are 758 m distant?
b. The centers of two lead spheres are separated by 4.90 m. If one sphere has a mass of 45.0 kg, and there is an attractive force of 1.20x10-9 N, what is the mass of the other sphere?
c. What is the velocity of the orbit that has a radius of 4.10x108 m around the earth? (m = 5.97x1024 kg)
d. You are in an orbit with a radius of 8.50x107 m and a period of 1.30x106 s around the planet Rjxnstdnnr. What is its mass?
Orbital Trajectory Videos:
Slow down at the x
Speed up at the x
Slow down at the x
Speed up at the x
Slow down at the x
Speed up at the x
In general, speeding up brings the far side out, slowing down brings the far side in. Speeding up brings the entire trajectory outside the old one, and slowing down brings entire trajectory inside the old one.
The Instruction for this unit:
Just doing calculations with gravity: (For some reason folks have had a hard time with this in the past, so maybe study this?)
Part 1 - Solving for Orbital Velocity given a radius:
Part 2 - Radius of Geostationary Orbit:
If you are having difficulty with solving orbit expressions for a certain variable, or want to know EXACTLY how to type it into the calculator, check out these two videos:
