根据短文判断下面各句正（T）误（F）。
There is a farm near my home. The farmers there grow rice and wheat. They have many animals on the
farm. But they don't use them to do farm work. They use a tractor. We often go to the farm after school. We
can play with the animals, walk, read books or help the farmers pick corn there. I like walking or doing some
reading on the farm because the air there is nice and clean.
You can see a lake on the farm. There are many fish in the lake. We often go fishing on Saturdays and
Sundays. We often swim in the lake in summer and skate on it in winter, too.
( ) 1. On the farm near my home, farmers use animals to do farm work.
( ) 2. I like reading books on the farm because there is a lake on it.
( ) 3. The air on the farm is very clean.
( ) 4. On Saturdays and Sundays, we often swim in the lake.
，开始由A点沿水平面滑至B点时速度为
，若该物块仍以速度
，已知斜面和水平面与物块的动摩擦因数相同，通过计算证明