The correct answer is
C. reduce the friction between its moving parts
In fact, by reducing the friction between the moving parts of the machine, it is possible to reduce the energy wasted due to this friction; therefore, more input energy is converted into useful work, and this will improve the efficiency of the machine.
Number 1. The medium around the wire
Electric force from electomagnetic force and force of gravity from gravitational force
We can't look at Figure 4. We don't know where a and b are. We can't see the blue shaded area. We don't know what our method above was. We can't see the green skinny rectangle.
To solve this problem it is necessary to apply the concepts related to the change of Energy in photons and the conservation of energy.
From the theory we could consider that the energy change is subject to
Where
Initial Energy
Energy loses
Replacing we have that
Therefore the Kinetic energy of the electron once it has broken free of the metal surface is 0.8eV
