题目

英语翻译
1.Work is done on an object only when a net force acts on the object to displace it in the direction of a component of the net force.
2.The amount of work done on an object by a force is equal to the component of the force along the direction of motion times the distance the object moves
3.Objects in motion have kinetic energy because of their mass and speed.
4.The net work done on or by an object is equal to the change in the kinetic energy of the object
5.Potential energy is energy associated with an object’s position.Two forms of potential energy discussed in this chapter are gravitational potential energy and elastic potential energy.
6.Energy can change form but can never be created or destroyed.
7.Mechanical energy is the total kinetic and potential energy present in a given situation.
8.In the absence of friction,mechanical energy is conserved,so the amount of mechanical energy remains constant
9.Power is the rate at which work is done or

提问时间：2021-01-25

答案

具体见下文：

几个分力对物体做功的代数和相当于这几个分力的合力对物体所做的功

一个力对物体所做功等于这个力去乘以在力的方向上物体所移动的距离

运动的物体具有动能是由于他们的质量与速度

合力（或其它物体）对一个物体做功等于这个物体动能的变化

势能与物体的位置有关.本章主要讨论势能的两种形式：重力势能与弹性势能

能量可以从一种形式转化为另一种形式但是在转化或转移中能量不能创造也不会凭空消失

在给定条件下,机械能即动能与势能之和

不考虑摩擦力,机械能守恒,所以总的机械能保持不变（为常数）

功率指的是做功或能量转移快慢的量（比率）

做相同的功,不同功率的机械装置所花时间不同.