The chair's mass is 18.8 kg. The force you exert on the chair is 160 N directed 26 degrees below the horizontal. While you slide the chair a distance of 6.20 m , the chair's speed changes from 1.50 m/s to 2.90 m/s . Find the work done by friction on the chair

To solve this problem it is necessary to apply the concepts related to energy conservation. Therefore, the work done will initially be equivalent to the change in kinematic energy. And this kinematic energy will be equivalent to the sum of energy (work) carried out by force and friction. In this way we have to

Now,

For each one we have

Then at the equation of equilibrium of energy we have,

Therefore the work done by friction on the chair is -833.7J

r=rho l/a where a is the area, l is the length and rho is resistivity so the greater the area the lesser the resistance thats why the earth pin is thicker bcos current follow the shortest path, so less resistive .

force required to detach it is given by

charges are taken to be fundamental charge

now we have

so above is the minimum distance at which it will detach