The combustion of 1 l of gasoline releases about 3.4×10^7j of energy. in one car's engine, about 80% of that energy is lost as heat. a. how much work is done by the engine for each liter of gasoline burned? (answer in mj/l)
b. if the car requires 5.9×10^5 j of work to travel 1 km, find the fuel efficiency in km/l.

A) The work done by the engine is: 6.8MJ/L

B) The fuel efficiency is

Explanation:

A)

We know that the gasoline releases about 3.4*10^7 J of energy for each liter, and about 80% of that energy is lost as heat; it means that the other 20% of the energy released is taken for the engine to do work. In that sense, the work done by the engine is 20% of the 3.4*10^7 J that the gasoline releases for 1 liter, so:

This last can be seen as a conversion factor, where we multiply the energy released by the gasoline by the factor (20 J taken for do work for each 100 J released).

B) We know that the car requires 5.9*10^5 J of work for each km traveled. That is the energy that the car requires, but it is not the energy that you have to give to the car; take in mind that the energy that you put in the car in gasoline liters will be not taken all, but just 20%. Also we know that the work done by the engine for 1 liter of gasoline is 6.8MJ, and that is just the work taken for do work (the useful energy), so we can connect both data:

The first fraction, is the ratio or the proportion of (1 km requieres 5.9*10^5 J); and we multiply by the second fraction , which is the ratio: 6.8*10^6 J of work done for each liter of gasoline.

b. lifting dumbbell weight at 20-degree angle from the body after a 45-degree angle

electromagnetic shielding is the practice of reducing the electromagnetic field in a space by blocking the field with barriers made of conductive or magnetic materials. shielding is typically applied to enclosures to isolate electrical devices from their surroundings, and to cables to isolate wires from the environment through which the cable runs. electromagnetic shielding that blocks radio frequency electromagnetic radiation is also known as rf shielding.

the shielding can reduce the coupling of radio waves, electromagnetic fields and electrostatic fields. a conductive enclosure used to block electrostatic fields is also known as a faraday cage. the amount of reduction depends very much upon the material used, its thickness, the size of the shielded volume and the frequency of the fields of interest and the size, shape and orientation of apertures in a shield to an incident electromagnetic

from wikipedia