How can submarines use echolocation to tell how close they are to the bottom of the ocean?

Sample Response: Submarines can release sound waves. These sound waves will hit the bottom of the ocean and be reflected back to the submarine as echoes. The submarine can use these echoes to tell how far it is from the bottom of the ocean.

Explanation: just answered this and this was the answer 100 percent  

a displacement distance is size of displ

weight of the box is given as

here this is placed on the inclined of angle 42 degree

now this weight will have two components one is along the incline other is perpendicular to it

so here we need to apply a force parallel to incline opposite to its component of weight

so here the component of weight is given as

here we have

so it requires 75 n force to move it upwards