because if you drop something,

因为你扔东西的话
it falls too fast for you to time it.

它会落得太快让你没法计时
But if you let it go down an incline,

但是如果让它从斜面上滑下来
by making θ very small

让 θ 非常小
so sin(θ) is very small and the grading is very low,

那么 sin(θ) 就非常小坡度就非常小
the body can accelerate with a much slower acceleration downhill,

物体就会以小得多的加速度下滑
because it's reduced by this factor, sin(θ).

因为加速度是按照这个因子减小的 sin(θ)
Okay, here's another thing I should tell you right now.

我还有一件事现在要告诉你们
Most of us, when we become professionals,

大多数人我说的是专业人士
don't put in numbers till the very end.

只在最后一步代入数值
So, if you are told the incline is an angle of 37 degrees,

如果已知斜面的倾角是 37°
g is 9.8, don't start putting numbers into the first equation.

g 等于 9.8 不要把数字代进第一个方程