S storeys Height of each storey=h Figure 2: A building of S identical stories, each of height h. b A building has S stories each of height h as shown in Fig.(2). An ex- plosion destroys the strength of the nth story. You may assume that the building remains intact above the story that explodes and that momentum is conserved in the collisions of the successive stories during the fall of the building. Estimate the time before the (n + 1)th floor hits the ground falling vertically.

What is the value of r of the geometric series?

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Aspacecraft can attain a stable orbit 300 kilometers above earth if it reaches a velocity of 7.7 kilometers per second. the formula for a rocket's maximum velocity v in kilometers per second is vequalsminus0.0098tplusc ln upper r, where t is the firing time in seconds, c is the velocity of the exhaust in kilometers per second, and r is the ratio of the mass of the rocket filled with fuel to the mass of the rocket without fuel. find the velocity of a spacecraft whose booster rocket has a mass ratio of 20, an exhaust velocity of 2.1 km/s, and a firing time of 15 s. can the spacecraft achieve a stable orbit 300 km above earth?