Answer:
1. Potential energy is converted into kinetic energy since they are in motion.
2. As they slope down, work is done against the dissipative forces e.g; Air resistance, viscosity ( friction ). Hence energy is lost.
3. Different weights and heights at which they started sloping.
[tex]potential \: energy = mgh[/tex]
where mg is the weight.
h is the height moved
therefore, weight and height determines the potential energy.