Naked Science Forum
General Science => General Science => Topic started by: newrobert on 17/11/2014 18:18:51
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Hi guy,
Please help me to understand that which forces help car still running even after switching off ignition or fan keep circulating even switching off button.
Thank you
Robert
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Hi guy,
Please help me to understand that which forces help car still running even after switching off ignition or fan keep circulating even switching off button.
Thank you
Robert
It's called pre-ignition. When hot spots develop in the combustion chamber, they will act like a glow plug igniting the air fuel mixture without the need of a spark from the spark plug. This is what happens when carbon deposits build up in the combustion chamber and also can happen when using inferior grades of fuel in high compression engines.
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Thank you for posting.
If 3 men are pushing a switched-off car and after some distance they stopped pushing car but the car still keeps moving for some distance, how that happened? Is there something rotational force involved or what?
In same sense even we switch off fan but still it keeps rotating for many seconds, although there is no powered being supplied, how this happened?
Robert
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Thank you for posting.
If 3 men are pushing a switched-off car and after some distance they stopped pushing car but the car still keeps moving for some distance, how that happened? Is there something rotational force involved or what?
In same sense even we switch off fan but still it keeps rotating for many seconds, although there is no powered being supplied, how this happened?
Robert
The laws of physics state that an object in motion will remain in motion until acted upon by a restraining force. In your first example, the car will continue rolling until the friction of the tire against pavement slows it to a stop. In the second example, the fan will continue rotation until friction in the fan motor and air resistance stops it also.
Consider the motion of a rocket in empty space where friction is as close to zero as one can imagine. It will travel on almost indefinitely.
BTW,..........welcome to the forum.
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Dieseling is another term for an engine that keeps running after the ignition is turned off. Diesel engines can actually run without electricity or sparks.
Most "modern" cars are required to have a fuel supply shutoff switch wired to the ignition, effectively preventing dieseling.
Higher Octane (premium) fuel may also help prevent dieseling.
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Some cars with a turbo compressor have a feature in the engine control software that lets the turbo cool down when you turn off the engine.
You take the key out of the ignition, lock the car, but the engine keeps idling for 30 seconds or so before turning off.
This feature reduces thermal shock in the turbo, and extends its life.