46. We neglect air resistance, which justifies setting a= –g= –9.8 m/s2(taking downas the –ydirection) for the duration of the fall. This is constant acceleration motion, which justifies the use of Table 2-1 (with Δyreplacing Δx).(a) Noting that Δy= y– y0= –30 m, we apply Eq. 2-15 and the quadratic formula (Appendix E) to compute t:ΔΔyvt gttvvgyg=−¡=±−02002122which (with v0= –12 m/s since it is downward) leads, upon choosing the positive root (so thatt
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