4. in the exploration, the sled does not move at all when two equal forces are applied
opposing directions. explain the reason behind this.

The net force is zero, so the acceleration is zero

Explanation:

Newton's second law states that the acceleration of an object is proportional to the net force applied to it, according to the equation:

(1)

where

is the net force on the object

m is the mass of the object

a is its acceleration

In this problem, we have a sled acted upon two forces, . So the net force on the sled is

(2)

however, we are told that the two forces are equal in magnitude but in opposite directions, so

So, eq.(2) becomes

and so eq.(1) becomes

which means

so the acceleration of the sled is zero, and if the sled was at rest, it will not move.

resonant frequency

thermal energy is the answer