Question

Astronauts visiting Planet X have a 2.6 -long string whose mass is 5.0g . They tie the string to a support, stretch it horizontally over a pulley 1.8m away, and hang a 1.8kg mass on the free end. Then the astronauts begin to excite standing waves on the string. Their data show that standing waves exist at frequencies of 64Hz and 80Hz , but at no frequencies in between.

What is the value of g , the free-fall acceleration, on Planet X?