Explanation :
Static friction is the frictional force between two objects that are at rest. While sliding friction is the frictional force between two objects in contact and are sliding w.r.t each other.
Static friction is usually greater than sliding friction because in static friction the contact forces is more and the interlocking between objects is tight as compared to sliding friction.
A mineral is a naturally occurring, inorganic solid with a definite chemical composition and a crystalline structure formed by geological processes.
A rock is an aggregate of one or more minerals. It may also contain organic remains and mineraloids apart from regular mineral formations. Since rocks vary in their mineral and chemical composition, they are classified according to the process of their formation.
Answer:
The alternative energy sources are defined as those resources that are used in place of the natural and non-renewable resources. This resources plays an important role in the conservation of natural resources.
The fossil fuels are the resources on which the people are directly dependent. Burning up of these fossils leads to the emission of carbon, which has a direct impact on earth. A small increase in the amount of carbon dioxide can lead to the increase in the surface temperature of earth.
In addition to this, these fossil fuels such as coal, petroleum, oil and natural gases are found to be present in a limited proportion, and it is a very expensive process to obtain these resources, so sustainable development method must be adopted in order to save this natural resources for the future generation.
Some of the examples of alternative resources that are widely used in place of fossil fuels are wind energy, solar energy, tidal energy, biomass energy and bio-fuels.
Thus, it is very important to develop and use alternative resources.
A gravitational force between objects depends on two things- their masses and the distance between them. So the greater the mass and the less distance there is, the more gravitational force and is the mass is less and the distance is great the gravitational force is weak
