83 Wrecking Ball vs. Strong Wall-Mid

Wrecking Ball vs. Strong Wall FOCUS Question How does a wrecking ball knock down a building?

破坏球vs强墙焦点问题破坏球是如何击倒一栋建筑的?

Demolition Day Have you ever tried to knock over a sand castle? Wrecking a weak building made of sand is easy. What if your job were to demolish a strong building made of brick and concrete? You could use a wrecking ball! Before knocking down an old building, workers first make sure that no one is inside. Then they bring a crane with a chain and a very heavy metal ball attached. This is a wrecking ball machine. Once the workers are sure that everyone is safe, they can swing the wrecking ball.

你试过拆掉沙堡吗? 摧毁用沙子建造的脆弱建筑很容易。 如果你的工作是拆除一座砖混结构的坚固建筑呢? 你可以用一个破坏球!在拆除一栋老建筑之前，工人们首先要确保里面没有人。 然后他们带了一个吊车，上面挂着链条和一个很重的金属球。 这是一台拆球机。 一旦工人们确定每个人都是安全的，他们就可以进行破坏。

Gravity Drop One way to use a wrecking ball is to drop it straight down. Think about holding a bowling ball. Suppose you could lift it over an old building and drop it straight down. It would smash through the roof! The higher the ball is lifted, the more damage it causes when it falls. This is due to gravity. Gravity always pulls things down. When an object falls gravity makes it fall faster and faster. An object that falls a long way moves with more energy than if it falls a short way. Dropping the wrecking ball straight down is often used to punch through roofs or floors.

使用破坏球的一种方法是让它垂直下落。 想象一下拿着一个保龄球。 假设你可以把它举过一座老建筑，然后直接扔下去。 它会砸穿屋顶的!球被抬得越高，下落时造成的伤害就越大。 这是由于重力。重力总是把东西往下拉。 当一个物体下落时，重力使它下落得越来越快。 一个物体下落较远的距离比它下落较短的距离运动的能量要大。 把破坏球直接扔下去通常是用来打穿屋顶或地板。

Tall Crane, Swinging Chain Another way to use a wrecking ball is to swing it. A cable pulls the ball toward the crane or the crane swings the ball away from the building. Then the ball swings forward and smashes into a wall. The force of this forward motion is how wrecking balls knock down walls. When a wrecking ball machine is used in this way, it acts as a pendulum.

另一种使用破坏球的方法是摆动它。 一根缆绳将球拉向起重机，或者起重机将球甩离建筑物。 然后球向前摆动，撞到墙上。 这种向前运动的力量就是破坏球击倒墙壁的力量。 当破坏球机以这种方式使用时，它起着钟摆的作用。

Pendulums A pendulum is an object that swings back and forth from a fixed point. It has a weight at the end of a line. When the pendulum is lifted and released, it swings back and forth in a curved path, or arc. At the top of its swing, gravity pulls the weight down. It speeds up as it goes down. After it passes the bottom part of its swing, the pendulum starts to move up along the arc. Gravity slows the pendulum down until it stops at the other end of the arc. Then gravity pulls it down again. It swings back in the other direction. A wrecking ball works in a similar way. But a wall gets in the way before the ball can make one full swing through its arc.

钟摆是一种从一个固定点来回摆动的物体。 它在直线的末端有一个重量。 当钟摆被举起和释放时，它会以弯曲的路径或弧线来回摆动。 在秋千的顶端，重力把重物拉下来。 它下降的时候会加速。 当钟摆经过摆动的底部后，钟摆开始沿着弧线向上移动。 重力使钟摆减速，直到它停在弧的另一端。 然后重力又把它拉下来。 它向另一个方向摆动。 破坏球的工作原理与此类似。 但在球完整地挥杆通过弧线之前，一堵墙挡住了它。

Wrecking Ball Energy A wrecking ball machine uses a lot of energy to demolish a building. Energy is the power to cause movement or change. When the ball swings away from the building, the machine has stored-up energy. Whoosh The wrecking ball swings. Thunk! The ball smashes into the wall. The building starts to crumble. A cloud of dust swirls into the air. Workers use other machines to haul away the rubble.

一台拆球机需要消耗大量的能量来拆除一座建筑物。 能量是引起运动或改变的力量。 当球离开建筑物时，机器就储存了能量。 嗖嗖，破坏球摇摆。 铛!球撞到墙上。 建筑开始倒塌。 一团尘埃在空中盘旋。 工人们用其他机器拖走瓦砾。