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The engine does work on the air going through it and this work is in the form of an increase in kinetic energy. The increase in kinetic energy comes from burning fuel and the ratio of the two is the thermal efficiency which equals increase in kinetic energy divided by the thermal energy from the fuel (fuel mass flow rate x lower calorific value).
The need to brake is sometimes caused by unpredictable events. At higher speeds, there is less time to allow vehicles to slow down by coasting. Kinetic energy is higher, so more energy is lost in braking. At medium speeds, the driver has more time to choose whether to accelerate, coast or decelerate in order to maximize overall fuel efficiency.
Gravitational time dilation is at play e.g. for ISS astronauts. While the astronauts' relative velocity slows down their time, the reduced gravitational influence at their location speeds it up, although to a lesser degree. Also, a climber's time is theoretically passing slightly faster at the top of a mountain compared to people at sea level.
If you travelled a year at 95% the speed of light; you'd age one year, and people on Earth would age 3.2 years! But if you were going 50% the speed of light it would only be 1.15 years. The effect ...
Low speed diesel engines like the MAN S80ME-C7 have achieved an overall energy conversion efficiency of 54.4%, which is the highest conversion of fuel into power by any single-cycle internal or external combustion engine. [9] [10] [11] Engines in large diesel trucks, buses, and newer diesel cars can achieve peak efficiencies around 45%. [12]
However, this does not imply that improved fuel efficiency is worthless if the Jevons paradox occurs; higher fuel efficiency enables greater production and a higher material quality of life. [19] For example, a more efficient steam engine allowed the cheaper transport of goods and people that contributed to the Industrial Revolution .
However, any gain to the rocket's kinetic energy is balanced by a relative decrease in the kinetic energy the exhaust is left with (the kinetic energy of the exhaust may still increase, but it does not increase as much). [2]: 204 Contrast this to the situation of static firing, where the speed of the engine is fixed at zero. This means that its ...
This figure does depend on the speed and mass of the rider: greater speeds give higher air drag and heavier riders consume more energy per unit distance. In addition, because bicycles are very lightweight (usually between 7–15 kg) this means they consume very low amounts of materials and energy to manufacture.