Fossil fuels are non-renewable resources and create greenhouse gases. While cheaper now to burn fossil fuels, within fifty years we will run out and have to turn to other sources of energy. Hope this helps!!!
For every reaction, there is an equal and opposite reaction. This means that with every interaction, theres a pair of opposite forces on the object.
Efficiency = 1000/2000 = 0.5 = 50%
The work-energy theorem says that the total work done on the block is equal to the difference of its kinetic energies at points B and A. Then the total work done on the block is
Friction acts on the block to oppose its motion, so it does negative work on the block, -4.5 J.
The only other force acting on the block as it moves is the force <em>P</em>. Let 
be the work done by the force <em>P</em>. Then the total work done on the block is
Answer:
Y = Stress / Strain = (F / A) / (l / L) where l is the change in length
Since L is doubled and A remains the same one would expect l, the change in length to also double so Y remains the same.
As an example think of hanging a weight from a spring and the same weight from a similar spring of twice the length - one would expect the longer spring to show twice the extension of the shorter spring.
