短文填词
A little child was playing one day with a very valuable vase.
He put his h________into it and could not draw
it back out.His father tried________vain to get
his hand out.They were thinking of breaking the vase
________(这时) his father said, "Now, my son,
try one more time.Hold your fingers out straight as you see me
d________and then pull."4.________
To________astonishment, the little fellow said.
"Oh no, father, I couldn't pull my fingers out like that because if
I did I________drop my penny." You may think it
is stupid________the boy to stick to penny at the
cost of his hand.Aren't we l________that little boy
sometimes?We are busy holding on to the world's
________(无价值的) penny that prevents us from
enjoying________(自由) belonging to us.
，方向水平向右，在O处放一个质量为m=0.1kg、带电量
的绝缘物块，它与水平面之间的动摩擦因数μ=0.2。现给物块一个水平向右的初速度
，(已知物块与水平面间的最大静摩擦力等于其滑动摩擦力，g取10m/s2)求: