Suppose you have a stack of 9 identical oak planks, each of which have a mass of 8.0 kg. You are required to pull the seventh plank from the stack (counting from the top). If the coefficient of friction between oak and oak is 0.6, how hard do you have to pull?
To determine how hard you need to pull the seventh plank, we need to consider the forces acting on the system.
The force required to pull the plank is determined by the frictional force between the seventh plank and the planks above it, as well as the weight of the planks above the seventh plank.
1. Calculate the weight of the planks above the seventh plank:
The weight can be calculated by multiplying the mass of a single plank by the number of planks above it.
Weight = mass × acceleration due to gravity
Weight = (8.0 kg) × (9 - 7) × (9.8 m/s²)
2. Calculate the frictional force:
The frictional force can be calculated by multiplying the coefficient of friction (0.6) by the normal force, which is equal to the weight of the planks above the seventh plank.
Frictional force = coefficient of friction × normal force
3. Determine the force required to pull the seventh plank:
The force required to overcome the frictional force is equal to the frictional force itself.
Force = frictional force
By following this step-by-step process, you can calculate the force required to pull the seventh plank.