K and M Current Photos

Here are some current photos of the railbridge near Pt. Pleasant.  There are several factors that go into bridge design and have a direct relationship with physical science.  Students should remember that Newton's 2nd and 3rd Laws must always be accounted for together when analyzing a situation.  Consider a train moving over the railbridge.  The train exerts a force on the bridge, its weight: F=ma (acceleration is gravity).  The bridge is in equilibrium, it is not falling or accelerating down.  Newton's 3rd Law helps to explain that the bridge must be appyling a force equal to and opposite in direction of the force the train applies and, their net force must be 0 so we say - Fnet = Ftr +Fbr = 0.  The acceleration due to gravity should have a negative sign for indication of direction.  This would be very appropriate for 9th graders.  11th and 12th graders could up the game by incorporating Hooke' Law: F = -kx and Young's Modulus: E = Stress/Strain.  I will discuss those on my next blog posting.