Rick Sharga from RealtyTrac says up to one-fourth of all homes that still have a mortgage loan balance are in this situation.

VOA: special.2011.01.24

Then we may, from this equation, say a certain force is acting in a given situation by multiplying the m times the a.

然后根据这个方程,我们就能说,得到给定条件下的作用力,它等于 m 和 a 的乘积

耶鲁公开课 - 基础物理课程节选