[填空题]
Ⅰ.The diagram below shows a water slide. As a test, an object is released from point $A$,$\,6.0\,m$ above the ground level. Point $B$ at the end of the slide is $2.0\,m$ above the ground level. Location $C$ is the point of contact of the slide with the ground. The slide approximates a circular shape at this point.
Air resistance and friction on the object are negligible.
1.Draw the free-body diagram of the forces acting on the object as it passes point $D$.
2.At the instant the object passes point $C$, explain why there is acceleration and yet no work is done.
Ⅱ.The object slides from point $A$ to point $B$ and is launched from point $B$ with an angle.
1.The speed of the object at point $B$ is approximately $m\;s^{-1}$
2.At point $B$, on the object is launched into the air and lands in a pool of water that is $2.2\,m$ below point $B$. After $1.1\,s$, it reaches the surface of the water. The angle $\theta$ of the launch above the horizontal is approximately $^{\circ}$.
3.Calculate the horizontal distance travelled by the object between losing contact with the slide and reaching the water. m
