Given the task definition, example input & output, solve the new input case.
Generate an overlapping word between the given two sentences. When you find the overlapping words, they don't have to match exactly, e.g., "survival" and "survive" are valid overlapping words. Little words like "the" or "of" don't count! You must generate significant words which are not the stop words.
Example: Sentence1: pesticides cause pollution. 
Sentence2: pollution can harm animals.
Output: pollution.
The word "pollution" is common to Sentence1 and Sentence2. So, it's a good answer.

New input case for you: Sentence1: sonar is used to find the location of an object. 
Sentence2: Surface ships use sonar to locate and track submarines.
Output:
location