To determine an athlete's body fat, she is weighed first in air and then again while she's completely underwater. It is found that she weighs 690 NN when weighed in air and 48.0 NN when weighed underwater. What is her average density

Two particles of masses m and 2m are placed on a smooth horizontal table. a string, which joins these two masses, hangs over the edge supporting a pulley, which suspends a particle of mass 3m.the pulley has negligible mass. the two parts of the string on the table are parallel and perpendicular to the edge of the table. the hanging parts of the string are vertical. find the acceleration of the particle of mass 3m.

=force × distance a. work b. velocity c. pressure d. momentum

What’s #16 asking me and how do i solve it?