There are three crates being pushed over a concrete floor by a horizontal force,There are three crates being pushed over a concret, of magnitude 440 N. The masses of the crates are m1=30.0 kg, m2=10.0kg, m3=20.0kg. The coefficient of kinetic friction between the floor and each of the crates is 0.700.

a. What is the magnitude F32 of the force on crate 3 from crate 2?
b. If the crates then slide onto a polished flow, where the coefficient of kinetic friction is less than 0.700, is magnitude F32 more than, less than or the same as it was when the coefficient was 0.700?

This problem involves the application of newtons third law of motion and the knowledge of frictional forces. The law which states that action and reaction are equal and opposite.

Explanation:

The approach to solving this problem draws the diagram that vonnects the three crates and sections the interconnection surface as can be seen below. The force of friction acts on each of the crates and is equal to uR where R is the reaction force of the ground on each of the crates.