Mammals that depend on being able to run fast have slender lower legs with flesh and muscle concentrated high, close to the body (Fig. 8–33). On the basis of rotational dynamics, explain why this distribution of mass is advantageous.

FIGURE 8-33 Question 6. A gazelle.

The distribution of mass in a gazelle is highly concentrated close to the body of the gazelle. The lower legs have fewer moments of inertia. So, less rotational inertia is required.

However, if the mass is uniformly distributed all over the body of a gazelle, the rotational inertia will be greater.

A gazelle’s body is designed in a manner such that the distribution of mass is on the higher side of the body. So, the moment of inertia is higher close to the body. However, the legs of the gazelle are slender lower. The legs have less distribution of mass. So, the moment of inertia of the legs is less. The rotational inertia of the legs is less.

For the same amount of angular acceleration, the gazelle requires less torque to run. Similarly, for the same amount of torque, the gazelle will run faster with high angular acceleration.

Thus, the distribution of mass of a gazelle will be advantageous for it because it can run faster with high angular acceleration for the same amount of torque.