Pour the entire components into water.
First the iron filings can be separated using a magnet as iron is a magnetic element.
By pouring the mixture into water, it allows the salt to dissolve in the water, while the sand will not.
Next we can run this solution through a filtration device to separate the sand from the water.
Now all that's left is to let the water evaporate so that the salt will be exposed that dissolved into the water.
If bonds are broken, the energy is released, and if bonds are formed, energy is absorbed. During conversions from chemical energy to thermal energy, the energy stored in the chemical bonds are released and this energy causes surrounding molecules to move faster thus increasing the thermal energy of a substance.
The net force on the hanging object is zero. If it were not zero, then the object would be accelerating in some direction.
The answer would be 27,000 Joules because (1/2) m v^2 =30*900 which equals 27,000 J