Question

An elephant's legs have a reasonably uniform cross section from top to bottom, and they are quite long, pivoting high on the animal's body. When an elephant moves at awalk, it uses very little energy to bring its legs forward, simply allowing them to swing like pendulums. For fluid walking motion, this time should be half the timefor a complete stride; as soon as the right leg finishes swinging forward, the elephant plants the right foot and begins swinging the left leg forward.


Question:

An elephant has legs that stretch 2.3m from its shoulders to the ground. How much time is required for one leg to swing forward after completing a stride?


I used T = 2pi*sqrroot(L/g) and got the period of 3.02. and also tried 1.52. Cant seem to find answer

Answer 1

It's actually 1.2 s and 97 steps/minute

Answer 2

The question tells us that the elephant's gait serves as a simple pendulum. From this information we can find the period of the stride inseconds/cycle.
Part 1:

T(Period)=2pvL/g
T=2pv2.3m/9.8m/s^2
T=3.04 seconds/cycle

--The question is a little ambiguous, I think. If it wants the time to complete a full stride, then the answer is 3.04seconds. If it want's the time thehalf step, the question says this should be half of a complete cycle, so 3.04s/2=1.52seconds.

Part 2:

To determine the frequency, we use this equation:

f=v(g/L)/2p
f=v(9.8m/s^2/2.3m)/2p
f=.82Hertz=.82cycles/second

The question asks how many steps the elephant will take in a minute, so convert the seconds to minutes:
0.82*cycles/second*60seconds/minute


To cancel the seconds:

.82(60)cycles/1minute=49.2cycles/minute

So, for every minute, the elephant will complete 49.2 cycles.

Answer 3

Answer #2 is correct. The question doesn't have enough information to answer as it requires the weight of the leg to solve it correctly.