Menu div.question,div.steps {font-size: 16px; padding: 10px;line-height: 20px; margin: 20px;} div.question{border: 1px solid #ccc;} div#solution .button{font-size: 20px; margin: 20px; width: 200px; padding: 10px; text-align: center;} div.hint,div.answer,div.steps{display: none;} div.pre_next{font-size: 30px; width:90%; margin:auto;} div.pre_next a.nav_pre{float:left;} div.pre_next a.nav_next{float:right;} div.title div.notes{ font-family:sans-serif, Arial; font-size: 18px; } 6. At time t = 0, a student throws a set of keys vertically upward to her sorority sister, who is in a window at distance h above. The second student catches the keys at time t. (a) With what initial velocity were the keys thrown? (b) What was the velocity of the keys just before they were caught? Hint v_f = v_i + at; x_f = x_i + v_it + 1/2 at^2 Answer (a) h/t + 4.90t (b)h/t - 4.90t Show Steps Givens: t y_i=0 y_f = h a = -g = 9.80 m//s^2 (a) y_f = y_i + v_it + 1/2 at^2 =>h = 0 + v_it -4.90t^2 => v_i = (h-0 + 4.90t^2)/t => v_i = color(red)(h/t + 4.90t) (b) v_f = v_i + at v_f = h/t + 4.90t +(-9.80)t = color(red)(h/t - 4.90t)