The strap wrench shown is used to grip the pipe firmly without marring the external surfac...

The strap wrench shown is used to grip the pipe firmly without marring the external surface of the pipe. Knowing that the coefficient of static friction is the same for all surfaces of contact, determine the smallest value of µs for which the wrench will he self-locking when a = 200 mm, r = 30 mm. and θ = 65°.