The number of particles is given by n = -D [2−1/ 2−1] are crossing a unit area perpendicular to x-axis in unit time. N1 and n2 are the number of particles per unit volume for the value of meant to be 1 2. What is the dimensional formula of diffusion constant D?

One hazard of space travel is debris left by previous missions. there are several thousand masses large enough to detect by radar orbiting the earth, but there are far greater numbers of very small masses such as flakes of paint. calculate the force exerted by a 0.110 mg chip of paint that strikes a space shuttle window at a relative speed of 5.00 ✕ 103 m/s and sticks, given the collision lasts 6.00 ✕ 10-8 s. such a collision chipped the window of the ill-fated challenger in june 1983, causing $50,000 of damage.