## Essential University Physics: Volume 1 (3rd Edition)

a) We consider the first meteoroid: $\frac{1}{2}mv^2-\frac{1}{2}mv_0^2=GMm(\frac{1}{R_E}-\frac{1}{r_1})$ $\frac{1}{2}v^2-\frac{1}{2}(2.1\times10^3)^2=GM_E(\frac{1}{6.37\times10^6}-\frac{1}{250,000,000})=1.12\times 10^4 \ m/s$ b) $\frac{1}{2}mv^2-\frac{1}{2}mv_0^2=GMm(\frac{1}{R_E}-\frac{1}{r_1})$ $\frac{1}{2}v^2-\frac{1}{2}(2.1\times10^3)^2=GM_E(\frac{1}{8500}-\frac{1}{250,000,000})=9.74\times10^3 \ m/s$