Question

In some movies where we see people in space, they sometimes show “gravity” being generated by rotating a cylindrical object at some rotational velocity. (a) Let’s say that this “space wheel” has a diameter of 165 m and a rotational period of 19 seconds. Based on this, what is the apparent gravity for someone walking on the walls? [5 points] (b) What is causing this artificial gravity? Further, we see this being effective for generating gravity in movies, but it is not useful in real life. Why not? Please help to put Michael Bay and Ridley Scott in their respective places!

Answer 1

(a) Given:

1. Diameter of "space wheel", d = 165 m

2. Period of rotation, T = 19 s

We know that in rotating circular bodies, the acceleration caused due to rotation is given by,

where is the angular velocity given by

Putting the values in the formula for a, we get,

Hence, the apparent gravity for someone walking on the walls will be 9.022 ms^-2.

(b) This artificial gravity is caused due to centripetal acceleration exerted on the walls of the "space wheel" to keep it rotating. When a person stands on the wall, the wall applies the force to keep them from flying away tangentially. This is similar to rotating a bead attached to a string. The only difference is that tension in the spring prevents bead from flying away tangentially.

Now, the use of artificial gravity might seem effective in movies but it is not useful in real life due to following reasons,

1. In smaller spacecrafts, the acceleration will be different on head and feet of the person. This will cause difficulties in walking. This can be solved by using larger spacecrafts.

2. Building a large spacecraft is not practical as building a large spacecraft requires a lot of materials. Even if we obtain these materials, with our current technology, it is still too expensive to send these materials in space in order to build the large spacecraft.