A 145 g baseball is dropped from a tree 8.0 m above the ground.(a) With what speed would it hit the ground if air resistance could be ignored?
(b) If it actually hits the ground with a speed of 8.40 m/s, what is the magnitude of the average force of air resistance exerted on it?
2007-03-16 10:34:59 · 2 answers · asked by Anonymous in Science & Mathematics ➔ Physics
(a)
Distance= 1/2 g t^2 = 4.9 t^2 = 8.0 m, so t = sqrt (8.0/4.9) = 1.3 seconds. The velocity as it hit the ground would be v = a t = 9.8 * 1.3 = 13 m/s (only two digits are significant).
(b)
Force = mv/t = 0.145 kg * v / 1.3 seconds = 0.11*v Newtons.
Compare the two forces at v=13 m/s and v=8.4 m/s.
2007-03-16 10:50:54 · answer #1 · answered by hznfrst 6 · 0⤊ 0⤋
There would be no average force of air resistance because you ignored air resistance in paragraph A.
2007-03-16 17:40:10 · answer #2 · answered by appsptspcl 4 · 0⤊ 1⤋