1.Gravity and jumping
For the same reason that people can jump up and down and planes can fly: power. Gravity is not of infinite strength. If it were, we wouldn't be able to do simple things, like raise our feet to walk or lift a book to read.
Gravity is powerful enough to ensure that things don't float around, but it's not strong enough to prevent them from leaving the surfaces on which they rest if an adequate force is applied to them.
Only a small amount of force or power is required to overcome the force attributable to gravity -- also known as weight. A swimming dolphin can easily produce enough power to generate enough speed to propel it through the surface of the water and continue through the air for a few meters. Thankfully, gravity is strong enough to ensure that what goes up must come down. Once the dolphin can no longer propel itself, it falls back into the ocean.
第一题的 leap该改为lead
2.Newton's first law of motion. In the absence of an external force, objects tend to keep moving in straight lines. When an object is loose on your dashboard, there is nothing tying it to the car's motion. It isn't really moving to the right, it's going in a straight line and the car is moving underneath it. Since you're going to the left with the car, it looks to you like the objects are moving right, but what they're really doing is staying on the original path before the turn.
好,作为一个诚实的孩子
我承认
我上google搜的
请求原谅