The crate moves at constant velocity, this means that its acceleration is zero, so the net force acting on the crate is zero (Newton's second law).
There are only two forces acting on the crate: the force F applied by the worker and the frictional force, acting in the opposite direction:

, where

is the coefficient of friction and

is the mass of the crate. Since the net force should be equal to zero, the two forces must have same magnitude, so we have:

And so, this is the force that the worker must apply to the crate.
Answer:
option D
Explanation:
The correct answer is option D
Potential energy of an object is because of its location.
Expression of potential energy
P E = m g H
where H is the height of the object.
g is acceleration due to gravity, 9.8 m/s²
m is the mass of the object.
Potential energy is directly proportional to the location of the object.
If the height of the object is more than the potential energy of the object will also increase.
The type of pipe wrenches <span>that </span>are<span> designed for turning and holding where marrying is not objectionable is called the chain </span>wrench.<span> This tool has two serrated that are adjusted to grip the pipe. This is very useful for those objects where marrying is not objectionable since this can be adjusted for that purpose. </span>