A. power plants burn coal. A fossil-fuel power plant is one that burns fossil fuels such as coal, natural gas or petroleum (oil) to produce electricity.
b. Fossil fuels are called so because they have been derived from fossils, which were formed millions of years ago during the time of the dinosaurs. They are fossilized organic remains that over millions of years have been converted to oil, gas, and coal.
C. they are generally classified as non-renewable resources because they take millions of years to form and known viable reserves are being depleted much faster than new ones are generated.
5.
a. Gravitational potential energy and work done
If an object is lifted, work is done against the force of gravity.
When work is done energy is transferred to the object and it gains gravitational potential energy.
If the object falls from that height, the same amount of work would have to be done by the force of gravity to bring it back to the Earth’s surface.
If an object at a certain height has 2000 J of gravitational potential energy, we can say that:
2000 J of work has been done in getting the object to that height from the ground
and
2000 J of work would have to be done to bring it back to the ground.
Explanation:
Natural length of a spring is 
. The spring is streched by 
. The resultant energy of the spring is 
.
The potential energy of an ideal spring with spring constant 
and elongation 
is given by 
.
So, in the current problem, the natural length of the spring is not required to find the spring constant .
∴ The spring constant of the spring = 
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The answer is A. Hope this helps!!!
Answer:
electrostatics
gravitational forces
Explanation:
rubbing the ballon leads to it acquiring charges that are opposite to that in the wall.the electostatic forces attract the ballon to the wall and tyhe gravitational pull later acts on the ballon causing it to fall down
