Science
A force is a push or a pull on an object.
力是对物体的推或拉。
A force changes the motion of a moving object.
力改变运动物体的运动。
A force can be strong or weak and it always has a direction.
力可以是强的，也可以是弱的，它总是有方向的。
The earth is a planet that goes around the sun in a circular orbit.
地球是一颗以圆形轨道绕太阳运行的行星。
The speed of its motion doesn't change, but the direction of its motion does.
它运动的速度不变，但运动的方向不变。
The earth has a layer of gas above its surface, which helps to support life.
地球表面有一层气体，有助于维持生命。
Atoms are the building blocks of matter.
原子是物质的组成部分。
At the center of an atom is its nucleus, which has a positive electric charge.
原子的中心是原子核，它带一个正电荷。
Outside the nucleus are electrons, which have a negative charge.
原子核外是带负电荷的电子。
Asteroids and comets, are objects that obey our sun, but are smaller than planets.
小行星和彗星是服从太阳的天体，但比行星小。
Asteroids that pass closed to the Earth are called near-earth objects.
靠近地球的小行星被称为近地天体。
The layer of gases just above Earth's surface is our atmosphere.
地球表面上的气体层就是我们的大气层。
The atmosphere is made up of gases, such as oxygen and nitrogen.
大气是由气体组成的，如氧和氮。
Without an atmosphere, there would be no life on Earth.
没有大气层，地球上就没有生命。
A force can increase or decrease the speed of an object, and it can change the direction of motion.
力可以增加或减少物体的速度，它可以改变运动的方向。
If they collide with Earth they could cause an extinction event.
如果它们与地球相撞，就可能导致灭绝事件。
The electric force between the nucleus and the electrons holds the atom together.
原子核和电子之间的电力能使原子结合在一起。
Geometry 几何学
The two lines on the left intersect each other at a right angle, which is 90 degrees.
左边的两条线以直角相交，也就是90度。
The two lines on the right are parallel, which means they never cross.
右边的两条线是平行的，这意味着它们永远不会相交。
The adjacent sides of a rectangle are perpendicular, which means they meet at a 90 degree angle.
矩形的邻边是垂直的，也就是说它们以90度角相交。
The opposite sides of a rectangle are equal and parallel, which means they never cross.
矩形的对边相等且平行，这意味着它们永远不会相交。
The area of a rectangle is the length times the width.
长方形的面积等于长乘以宽。
A circle is a two dimensional figure with a radius and circumference, which is the distance around the circle.
圆是一个具有半径和周长的二维图形，也就是绕圆的距离。
The area of a circle is PI R squared, well, R is the radius and PI is the ratio of a circle circumference to its diameter.
圆的面积是R方，R是半径是圆的周长和直径的比值。
A sphere is a three dimensional figure with a radius and a volume, which is 4/3 PI R cubed.
球是一个三维图形，半径和体积，是4/3 R³。
All points on the surface of a sphere are equidistant from its center.
球面上的所有点离圆心的距离都相等。
A right triangle is a two dimensional figure with 3 sides, two of which are perpendicular.
直角三角形是一个二维图形，有三条边，其中两条是垂直的。
To find its area, multiply the length of the two perpendicular sides, A & B, and divided by two, A equals one half A B.
要找到它的面积，乘以两条垂直的边A和B的长度，然后除以2,A等于1 / 2ab。
A rectangle is a two dimensional figure with 4 sides.
长方形是有四条边的二维图形。