0.02. 5. A scientist is trying to calculate the coefficient of static friction for rubber on wood. He uses a 3.0 kg rubber block and a spring scale and notices that the maximum force on the spring scale reads 25 N before the block starts moving, and reads 21 N after the block starts moving. What is the coefficient of static friction? child sits on a stationary sled. How much force is required to push the child and sled in motion if their