Any motion that is regular and repeating is referred to as a periodic motion. most objects that vibrate do so in a regular and repeated fashion much like this spring seen here. according to newton's 1st law of motion,
a) the greater the mass of the spring, the greater the periodic motion.
b) the lower the mass of the spring, the faster the repeating motion occurs.
c) the periodic motion will continue forces acting on the spring are unbalanced.
d) there is an equal and opposite reaction force that slows down the periodic motion.

Arunner is jogging at a steady 3.6 km/hr. when the runner is 2.9 km from the finish line, a bird begins flying from the runner to the finish line at 14.4 km/hr (4 times as fast as the runner). when the bird reaches the finish line, it turns around and flies back to the runner. even though the bird is a dodo, we will assume that it occupies only one point in space, i.e., a zero-length bird. how far does the bird travel? (b) after this first encounter, the bird then turns around and flies from the runner back to the finish line, turns around again and flies back to the runner. the bird repeats the back and forth trips until the runner reaches the finish line. how far does the bird travel from the beginning? (i.e. include the distance traveled to the first encounter)