Use a light spring with original length l0 = 15cm to lift a wooden block vertically, and the length of the spring is L1 = 23cm. If the wooden block is pulled horizontally to move uniformly on the horizontal table, the length of the spring is L2 = 17cm. Calculate the dynamic friction coefficient u between the wooden block and the horizontal table. If the mass of the wooden block is m = 8kg, what is the light coefficient K of the spring?

Use a light spring with original length l0 = 15cm to lift a wooden block vertically, and the length of the spring is L1 = 23cm. If the wooden block is pulled horizontally to move uniformly on the horizontal table, the length of the spring is L2 = 17cm. Calculate the dynamic friction coefficient u between the wooden block and the horizontal table. If the mass of the wooden block is m = 8kg, what is the light coefficient K of the spring?

Stiffness coefficient of spring k = f / △ x = g / △ x = 8 * 10 / (23-15) * 10 ^ - 2 = 1000N / M
The spring is used to pull the block horizontally and move uniformly on the horizontal table
F=（17-15）*1000/100=20N
umg=20N
u=20/(8*10)=0.25