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动量定理反映了物体在某一过程中所受合外力的冲量与它的动量变化之间的关系,即F△t=△p=mv-mv0. 用动量定理解决打击、碰撞等短时间作用问题要比牛顿第二定律方便得多.如果在思维方式和理解上加以拓展,其适用范围会更广,用起来也更灵活. 1.用动量定理解流体问题 例1 坑道采煤机主要用高压水枪进行,设水的密度为ρ,水枪口的横截面积为S,水从枪口喷出时的速度为v,水平直射煤层后速度变为零,则煤层受到水的平均冲击力
The momentum theorem reflects the relationship between the external force of an object and its momentum change in a certain process, that is, FΔt=Δp=mv-mv0. Use momentum theorem to solve short-term problems such as impact and collision. It is much more convenient than Newton’s second law. If you expand the way of thinking and understanding, the scope of application will be wider and more flexible. 1. Use fluid momentum to understand fluid problems. Example 1 The main use of high pressure coal pit shearer The water gun is used to set the water density to ρ, the cross-sectional area of the water gun mouth to S, and the speed at which the water is ejected from the muzzle to v. After the horizontal straight coal seam speed becomes zero, the average impact force of the coal seam is affected by the water.