[填空题]
A 145-g baseball is dropped from a tree 13.0 m ab0e53qc pq3 hiuove the grou98o7ls4a1,w m sm1l 0 a mnk t:eoqqi)nd+psl8nd.
(a) With what speed would it hit the ground if air resistance could be ignored? m/s
(b) If it actually hits the ground with a speed of 8m/s what is the average force of air resistance exerted on it? N