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# A stone is thrown straight downward with a speed of 20 ms from the top of a tall building If the stone strikes the ground 30 s later about how tall is the building Assume air resistance is

A stone is thrown straight downward with a speed of 20 m/s from the top of a tall building. If the stone strikes
the ground 3.0 s later, about how tall is the building? Assume air resistance is negligible.
(A) 45 m (B) 60 m (C) 90 m (D) 105 m (E) 120 m
68. A coyote can run at a speed of 20 m/s while a prairie dog can manage only 5.5 m/s. If a prairie dog is 45 m in
front of a coyote, what is the maximum time it has to reach its hole without being caught?
(A) 2.3 s (B) 3.1 s (C) 5.4 s (D) 5.9 s (E) 8.2 s
69. A model rocket accelerates from rest upwards at 50 m/s2
(A) 100 m (B) 510 m (C) 610 m (D) 1020 m (E) 1220 m
for 2.0 s before its engine burns out. The rocket then
coasts upward. What is the maximum height that the rocket reaches? You may assume air resistance is
negligible.
70. A hunter in a forest walks 800 m west. He then turns south and walks 400 m before turning west again and
walking a final 300 m. At the end of the walk, what is the magnitude of the hunter's displacement from the
beginning?
(A) 640 m (B) 890 m (C) 1170 m (D) 1390 m (E) 1500 m

Jun 20 2020 View more View Less