Slides (滑梯) are simple but always fun. All you need to do is to climb up to the top and slide down. But did you know that there is science behind it?
Do you like science? Newton said what goes up must come down. He was talking about gravity (重力). Slides work because of gravity. But that is not all. |
| When you sit at the top of a slide, you stay still unless you push yourself—this is Newton’s first law. As you slide down, friction (摩擦力) between your body and the slide slows you down a bit. Without friction, you would slide faster and faster. At the bottom, your feet touch the ground, creating extra (额外的) friction to stop you. Newton’s first law also says moving things keep moving unless something makes them stop. So, if you do not use your feet, you’ll fly off the slide. |
21．What will happen if you don’t use your feet at the bottom of the slide according to Newton’s first law?
A．You will fly off the slide.
B．You will slide back up.
C．You will stop immediately.
D．You will stay at the bottom.
22．Which picture explains why you slow down a bit when sliding down?
A．
B．
C．
D．
23．Where can we probably read the text?
A．In a storybook.B．In a science book.
C．In a school poster.D．In a guidebook.
