Modeling Friction Forces

Today, we do this lab because we want to find the friction and the the relation of friction. We use four steps to find the static friction, the kinetic friction static friction with angle and the kinetic friction from sliding block down and incline.

In this case, my partner and I put water into the cup and pull the block which we let slide the surface of table, If the static friction is bigger than the pulling force, the block will not move, because we all know the maximal static friction is always the constant friction, so there is the maximal static friction when the block suddenly moves. We put the different weight of block on the table: the original and add others, we get different water's weight. If we set the pulley is friction-less, the weight of water is the static friction when the block suddenly move. As the coefficient of static friction equation what I show on the picture, we can get the answer that are o.3697, 0.3358, 0.3139, 0.2997.

On this case,we try to find the kinetic friction, so we pull the block with the constant speed. because the constant speed, the acceleration is zero, it means the pulling force is the kinetic friction because function F-F(k)=ma. By the way, the blocks' mass is same as the blocks of static friction. We get the coefficient of kinetic friction are 0.337, 0.3427, 0.286 and 0.282.

This step show how to find the coefficient of kinetic friction. We find that if the theta is 29 degree, the speed of the slide is constant, then the F=f(k), then the  is tan(theta) is 0.38.

on this case we use a 0.1 kg gram to pull the block on the table, if we set the pulley is friction-less, the acceleration will be a= (Mg-mg )/(M+m). we know the  =0.38, M=0.1 and m=0.1322. Then we get the acceleration is 2.065.