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Homework Statement
All walking animals, including humans, have a natural walking pace, a number of steps per minute that is more comfortable than a faster or slower pace. Suppose this natural pace is equal to the period of the leg, viewed as a uniform rod pivoted at the hip joint. A) How does the natural walking pace depend on the length L of the leg, measured from hip to foot? B) Fossil evidence shows that Tyrannosaurus rex, a two-legged dinosaur that lived about 65 million years ago at the end of the Cretaceous period, had a leg length L = 3.1 m and a stride length (the distance from one foot-print to the next print of the same foot ) S = 4.0 m. Estimate the walking speed of Tyrannosaurus rex.
Homework Equations
I=(m*L^2)/3
T=2*pi/w
The Attempt at a Solution
T=2*pi/w=2*pi/sqrt(Lmg/I)
I=(m*L^2)/3
T=pi*sqrt(4L/3g)=2.04s
v=s/T=4m/2.04s=1.96m/s
But the answer says that T=2pi*sqrt(2L/3g)=2.88s
v=s/T=4m/2.88s=1.4m/s