If we decrease the distance traveled over the same period of time, this will

The decrease in distance over same time period will decrease the speed.

Explanation:

Speed is defined as the amount of distance traveled in unit time or it is the ratio of distance traveled by Time taken.

Mathematically,

Where, v = speed of the object

s = distance traveled by the object

t = Time taken by the object

From the above relation, speed is directly proportional to the distance and inversely proportional to the time period.

In the given question, time period remains the same and the distance is decreasing.

This will result in the decrease of speed of an object as distance is directly proportional to the speed. So, increase in distance will increase the speed and vice-versa.

Hence, the decrease in distance over same time period will decrease the speed.

the part of the wave he is travelling on is the crest