Chapter 10, Problem 99A

To determine

To find: The efficiencies of the parts of the power train (engine, transmission, wheels, and tires).

To explore:The possible improvements in each of these efficiencies.

Explanation of Solution

Formula used:

The equation for the power needed to do work on the system is

  $P=\frac{W}{t}$  ......(1)

Here, $W$ is the work done on the system and $t$ is the time needed to complete the work.

The work done on the system through a distance is given by the equation,

  $W=Fd\cos \theta$  ......(2)

Here, $F$ is the applied force, $d$ is the displacement and $\theta$ is the angle between the force and displacement vector.

Calculation:

If the displacement vector and the force are in the same direction, that is, $\theta =0°$ then the equation for the work would be

  $W=Fd$  ......(3)

The equation for the power would change to

  $P=\frac{Fd}{t}$  ......(4)

The efficiency of the engine depends upon the work output over the work generated by the engine.

The transmission efficiency of fuel to the engine is close to 90 % or above. The friction force that opposes the motion of the engine is reduced by the rolling so, the efficiency loss would be like 1 % due to the wheels and tires. The efficiency of the engine is significant than the changes in the efficiency of transmission, wheel, and tiers in an automobile.

Conclusion:

Hence, the efficiency of the engine is significant than the changes in the efficiency of transmission, wheel, and tiers in an automobile.