1. The problem statement, all variables and given/known data A thin uniform 12.0-kg bar that is 2.00 m long rotates uniformly about a pivot at one end, making 5.00 complete revolutions every 3.00 seconds. What is the kinetic energy of this bar? (Hint: Different points in the bar have different speeds. Break the bar up into infinitesimal segments of mass dm and integrate to add up the kinetic energy of all these segments. 2. Relevant equations K=Integral of 1/2 times dm v^2 dm=M/L *dx 3. The attempt at a solution I got stuck when trying to substitute dm for M/L*dx. why does dm/dx=M/L if M is the mass of the entire bar and L is the length of the bar?