<span>These protrusions will only bind to </span>certain<span> receptors on the host cell; they are essential for both host specificity and viral infectivity.</span>
If the mass of both of the objects is doubled, then the force of gravity between them is quadrupled; and so on. Since gravitational force is inversely proportional to the square of the separation distance between the two interacting objects, more separation distance will result in weaker gravitational force
