Question

在沙堆上放一木塊（質(zhì)量為M=5 kg),木塊上放一爆竹（質(zhì)量為m=0.10 kg).點(diǎn)燃爆竹后由于爆炸木塊陷于沙中5 cm.若沙對運(yùn)動木塊的阻力為58 N，不計(jì)爆竹中火藥的質(zhì)量和空氣阻力.求爆竹上升的高度.（g=10 m/s²)

Answer 1

答案：
解析：

解析：爆竹爆炸時(shí)爆竹和木塊動量守恒.取向上為正方向，由動量守恒定律得： mv+(-MV)=0                                                                                                           ① (式中v、V分別是爆炸后爆竹和木塊速度） 木塊陷于沙中，做勻減速運(yùn)動，由動能定理得： 0-MV2=-（F-Mg）s                                                                                             ② 爆炸后爆竹以v做豎直上拋運(yùn)動，設(shè)達(dá)到的高度為h，則： 0-v2=-2gh                                                                                                                ③ 由②得V=0.4 m/s                                                                                                    ④ ④代入①得v=20 m/s                                                                                              ⑤ ⑤代入③得h=20 m