Two girders are made of the same material.Girder A is twice as long as girder B and has a cross-sectional area that is twice as great.The ratio of the mass density of girder A to the mass density of girder B is:
A)4
B)2
C)1
D)1/2
E)1/4

Question

Quizplus · Accepted Answer

The mass of each girder is directly proportional to its volume, which is proportional to its length and cross-sectional area. Girder A is twice as long and has twice the cross-sectional area, so its volume is four times that of girder B. However, since they are made of the same material, their densities (mass per unit volume) must be equal. Therefore, the ratio of the mass density of girder A to that of girder B is 1.

Two Girders Are Made of the Same Material