Our model says that-

• Friction is independent of surface area.
• The frictional force is only dependent on the normal force.
• The maximum static frictional force is given by F_SF= m_s F_N
• The kinetic frictional force is given by F_KF= m_K F_N

You push horizontally on a 35 kg crate with a 110 N force.  The coefficient of static friction between the crate and the floor is 0.37.

• Does the crate move?
• What is the frictional force exerted on the crate by the floor?
• What is the maximum magnitude of the static frictional force under the circumstances?
• Suppose, that a classmate pulls directly upward on the crate to help out.  What is the least pull that they can exert that will allow the your push to move the crate?
• If, instead, your friend pulls horizontally to help out, what is the least pull they can exert to get the crate moving?