题目

if a 1500kg car moving with velocity of 50m/s is suddenly decelerate to a stop.its acceleration during this period is -10m/s2,and it takes 50m for the the car come to a complete stop.the coefficient of the friction is 0.8.
if i want to calculate the force of the friction,which formula should i use?F=Ma or f=N*µ?why?what's the difference?will these two results come up to be the same?(i make up those data)

提问时间：2020-10-29

答案

问题很简单.两个公式的应用条件是不同的,第一个是牛顿第二定律的表达式,力为物体在运动的过程中受到的合外力,加速度是合加速度.用此公式去此题结果是15000N.而第二个公式是第三章学的求摩擦力的公式,此公式中的力N是...