汽车的两种启动方式一直是学生容易混淆的问题.下面就此问题做些分析归纳以帮助同学们理解运用.首先要明确功率要具体到什么力的功率,而力的存在当然离不开物体.当我们谈到发动机的功率时,要明确发动机对汽车提供的是一个与前进方向相同的牵引力,即发动机的功率也就是牵引力的功率,而不是随意的一个力的功率,当然也不是汽车所受合外力的功率.在两种启动方式中,关键要抓住不变的物理量去分析理解汽车的运动性质.下面以汽车在水平路面上的启动为例说明.一、以恒定功率启动例1质量为5t的汽车在水平公路上行使,阻力是车 The two ways to start the car has always been a student confusion .Following this issue to analyze and summarize to help students understand and use .First of all to clear the power to be specific to what power, and the existence of force, of course, inseparable from the object. When we talk about the power of the engine, we must make clear that the engine provides the car with the same traction as the forward direction, that is, the power of the engine, that is, the power of the traction, not the random power of one force, and certainly not the car In the two start-up mode, the key to seize the same physical quantity to analyze and understand the motor properties of the car below to the car on the level of the road as an example to illustrate the first, with a constant power to start Example 1 mass For the 5t car exercise on the horizontal road, the resistance is the car