Estimate the magnetic field strength required at the LHC to make 7.0-TeV protons travel in a circle of circumference 27 km. Start by deriving an expression, using Newton's second law, for the field strength B in terms of the particle's momentum p, its charge q, and the radius r. Even though derived using classical physics, the expression is relativistically correct. (The estimate will come out much lower than the actual value of 8.33 T. In the LHC, the protons do not travel in a constant magnetic field; they move in straight-line segments between magnets.)