Energy as a tool for mechanics problem solving能量作为力学问题求解的工具
The application of the conservation of energy principle provides a powerful tool for problem solving. Newton's laws are used for the solution of many standard problems, but often there are methods using energy which are more straightforward. For example, the solution for the impact velocity of a falling object is much easier by energy methods. The basic reason for the advantage of the energy approach is that just the beginning and ending energies need be considered; intermediate processes do not need to be examined in detail since conservation of energy gaurantees that the final energy of the system is the same as the initial energy. 应用能量守恒原理提供了一个强大的问题求解工具。牛顿运动定律被用于解决许多标准问题，但常常有更简便的方法使用能量方法。例如，求坠落物体的撞击速度时，使用能量方法要简单得多。能量方法的优势基本原因在于，只需考虑初始和最终的能量；无需详细考察中间过程，因为能量守恒保证了系统的最终能量与初始能量相同。
The work-energy principle is also a useful approach to the use of conservation of energy in mechanics problem solving. It is particularly useful in cases where an object is brought to rest as in a car crash or the normal stopping of an automobile. 力学中，功-能原理也是在解决力学问题时应用能量守恒的一个有用方法。特别是在物体因碰撞而停止的情况下，如汽车碰撞或汽车正常停车时，这种方法特别有用。
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Object Falling from Rest从静止下落的物体
As an object falls from rest, its gravitational potential energy is converted to kinetic energy. Conservation of energy as a tool permits the calculation of the velocity just before it hits the surface. 当物体从静止下落时，其引力势能转化为动能。能量守恒作为工具，可以用来计算物体触地前的瞬时速度。
 Since you know velocity, mass, and kinetic energy, can you predict the force of impact?既然你知道速度、质量和动能，能否预测冲击力？ |
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