用所给词的适当形式填空。

1.  It isn't easy_____ (learn) English well.

2.  His brother wants to be an_____ (act) when he grows up.

3.  The price of the TV is the _____ (high) of all.

4.  Bill Gates won a great_____ (successful).

如图所示，将载有条形磁铁的两辆小车同时由静止释放后，两小车将迅速分离。此现象包含的力学知识有（选填两点）：①_____________、②_______________。