physic物理问题英文81.wouldyouratherbehitbya1-kilogrammasstraveling10meterspersecond,ora2-kilogrammasstraveling5meterspersecond?2.Comparedtoacarmovingat10milesperhour,howmuchkineticenergydoesthatsamecarhave

Question

physic物理问题英文8
1.would you rather be hit by a 1-kilogram mass traveling 10 meters per second,or a 2-kilogram mass traveling 5 meters per second?
2.Compared to a car moving at 10 miles per hour,how much kinetic energy does that same car have when it moves at 20 miles per hour?at 30 miles per hour?at 60 miles per hour?what do these numbers suggest to you about the difficult of stopping a car as its speed increases?
我想要答案.英文中文都可以.

Answer 1

1.两种情况下,动量相同,但是动能前者大.所以尽管不想被任何一个击中,但如果非得选一个的话,选第二个好了.
2.设汽车10miles per hour行驶时的动能为W
则,由W=0.5*m*v^2知
20 miles per hour时,动能为4W
30 miles per hour时,动能为9W
60 miles per hour时,动能为36W.
可以看出,动能是与速度的平方成正比的.所以,速度越快,停下来需要的能量就越大.