Changing Gears & Vehicle Speed: Exploring the System

In summary, when driving a geared vehicle, you can vary the speed by changing gears. The engine speed increases as you increase the pressure in the engine, which in turn increases the drive thrust and speeds up the car. The gears are used to vary the velocity ratio, while the power and torque delivered by the engine depend on the amount of charge injected into the cylinder. Each gear has a speed limit, and the vehicle can only run in a certain gear when it reaches a certain speed. The maximum and minimum values of torque produced by the engine are independent of the gears, as they are only used to vary the velocity ratio.
  • #1
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When you are in a particular gear (say 2nd) , you can vary the speed of vehicle. So what actually is varied in the system as you are not changing the gear, iis it the amount of charge or rpm of the engine is varied to increase speed in a particular gear?

Also while changing gears, does the rpm of engine changes or amount of charge coming in increases or something else increases...?
 
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  • #2
You will have heard this every time you travel in a geared vehicle. Every time the gear increases the engine note drops, indicating that the rpm drops, but each 'cog' moves the axles by a greater amount. Does that help?
 
  • #3
Sorry if can elaborate more it will be of great help for me
 
  • #4
actually the gearbox is the combination of the different gear wheels with different diameter thus having the different no. of teeths.
the gear wheel of the first gear is large amoung all gear wheels and thus having the larger no. of teeths and moving from ist gear to top gear the diameter of the respective gear wheels decreases and thus the no. of teeths decreases.
speed of the gear wheel in rpm is inversely proportional to the no. of teeths higher the no. of teeths lesser will be the speed in rpm and vice versa.
the maximum and minimum value of the torque produced by the engine is independent upon the gears , gears are only used to vary the velocity ratio and nothing else, the power and torque delivered by the engine depends upon the amount of charge injected inside the cylinder portion both in case of the petrol or diesel engine i.e, more we press the accelerator pedal more fuel will be injected inside the cylinder and more combustion occurs thus producing the thrust and hence toque on the crankshaft.
if we press the accelerator full either in 1st gear or 5th gear same power is delivered by the engine.
there is a speed limit for each gear just like :
1st gear - 0 to 10 kmph
2nd gear - 10 to 35 kmph and so on... ( depending upon the gearbox)
thus vehicle can only run in certain gear ( say 2nd) when it attains the speed ( greater than 10) else it will try to stop the engine automatically.

i hope u understand what u want ..
 
  • #5
sk1329 said:
When you are in a particular gear (say 2nd) , you can vary the speed of vehicle. So what actually is varied in the system as you are not changing the gear, iis it the amount of charge or rpm of the engine is varied to increase speed in a particular gear?

Also while changing gears, does the rpm of engine changes or amount of charge coming in increases or something else increases...?

You increase the pressure in the engine, which increases the drive thrust and speeds up the car, the result being the engine speed rises.
 

1. What is the purpose of changing gears in a vehicle?

Changing gears in a vehicle allows the engine to operate at its most efficient speed for a given driving situation. This can improve fuel efficiency, acceleration, and overall performance of the vehicle.

2. How does changing gears affect vehicle speed?

Changing gears allows the driver to control the speed at which the vehicle is moving. By shifting to a higher gear, the engine works less to maintain the same speed, resulting in a higher vehicle speed. Shifting to a lower gear can slow down the vehicle by increasing the engine's workload.

3. What is the difference between automatic and manual transmission?

An automatic transmission shifts gears automatically based on the vehicle's speed and the driver's input. A manual transmission requires the driver to manually shift gears using a clutch and gear stick.

4. How do I know when to change gears in a manual transmission?

In a manual transmission, the driver should change gears when the engine reaches a certain RPM (revolutions per minute). This is typically indicated on the vehicle's tachometer. Shifting too early or too late can result in decreased performance and potential damage to the engine.

5. Can changing gears improve the lifespan of a vehicle?

Properly changing gears and maintaining a consistent speed can reduce wear and tear on the engine and other components of a vehicle, potentially extending its lifespan. However, aggressive driving and improper gear shifting can have the opposite effect and decrease the lifespan of a vehicle.

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