[填空题]
A 140-kg astronaut (includ7s l j6hxf36 x;;k4ls-o skb ksip)md7ing space s0 zoboft x8wp).; lmt4uit) acquires a speed of 2.5m/s by pushing off with his legs from an 1800-kg space 40.lp8ow)x zt; mto bfcapsule.
(a) What is the change in speed of the space capsule? m/s
(b) If the push lasts 0.40 s, what is the average force exerted on the astronaut by the space capsule? As the reference frame, use the position of the space capsule before the push. N
