You observe two galaxy clusters, cluster A and cluster B.If the outer galaxies of both clusters have the same circular velocities, but cluster A has twice the mass of cluster B, then the size of cluster A must be
A) 4 times that of cluster B.
B) one-fourth that of cluster B.
C) twice that of cluster B.
D) half that of cluster B.
E) the same as cluster B.

Question

Quizplus · Accepted Answer

The circular velocity of galaxies in a cluster is determined by the balance between gravitational force and centripetal force. If cluster A has twice the mass of cluster B but the same circular velocity, then the radius of cluster A must be twice that of cluster B to maintain this balance.

You Observe Two Galaxy Clusters, Cluster a and Cluster B