The elastic potential energy of a spring is given by

where k is the spring's constant and x is the displacement with respect to the relaxed position of the spring.
The work done by the spring is the negative of the potential energy difference between the final and initial condition of the spring:

In our problem, initially the spring is uncompressed, so

. Therefore, the work done by the spring when it is compressed until

is

And this value is actually negative, because the box is responsible for the spring's compression, so the work is done by the box.
Answer:
The distance from Witless to Machmer is 438.63 m.
Explanation:
Given that,
Machmer Hall is 400 m North and 180 m West of Witless.
We need to calculate the distance
Using Pythagorean theorem

Where,
=distance of Machmer Hall
=distance of Witless
Put the value into the formula


Hence, The distance from Witless to Machmer is 438.63 m.
where are the answer choises
Answer:

Explanation:
Given data:



Let the distance traveled by the object in the second case be 
In the given problem, work done by the forces are same in both the cases.
Thus,





Answer:
Ionic compound.
Explanation:
812° C is a very high melting point. Such high melting points are generally ionic compound. Ionic compounds are have very strong bond between the elements ( electrostatic bond). In order to break this bond, large amount of heat energies are needed. So, they have high melting point. Also, Ionic compound are very good conductors of electricity.