What acceleration produces one gravity force?
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He's actually asking for miles/hour/second. Yup, what a nutty unit.Humus said:
And I just took the physics part on the SAT2 and don't feel like answering any physics questions again. Ever.
1g in terms of mph/sec is appx 21.9 mph/sec.
However I can see very little use for expressing it in this fashion. It's easily enough derived by multiplying 9.8 meters by 3600 seconds to determine speed in meters per hour. You then divide by 1609.3 (meters in a mile) to get an answer.
Acceleration is a scalar quantity, not a vector quantity, which means it's not dependent on direction. It measures total change in speed regardless of which way. So an object will feel the same force from the same amount of acceleration as deceleration because they are the same thing. Deceleration doesn't actually exist in and of itself, it's just a term we use to refer to an acceleration used to counter a previous acceleration and because people don't feel comfortable with the fact that an acceleration can actually slow you down.
PS: mph is a measure of speed, not velocity. Speed is the scalar, velocity the vector. Velocity is speed plus direction.
However I can see very little use for expressing it in this fashion. It's easily enough derived by multiplying 9.8 meters by 3600 seconds to determine speed in meters per hour. You then divide by 1609.3 (meters in a mile) to get an answer.
Acceleration is a scalar quantity, not a vector quantity, which means it's not dependent on direction. It measures total change in speed regardless of which way. So an object will feel the same force from the same amount of acceleration as deceleration because they are the same thing. Deceleration doesn't actually exist in and of itself, it's just a term we use to refer to an acceleration used to counter a previous acceleration and because people don't feel comfortable with the fact that an acceleration can actually slow you down.
PS: mph is a measure of speed, not velocity. Speed is the scalar, velocity the vector. Velocity is speed plus direction.
Rugor said:
No, acceleration is not a scalar - it is a vector. Acceleration is the derivative of velocity, and velocity is a vector; hence, acceleration is a vector. Hence the existance of centripetal acceleration - where you can be moving at a constant, unchanging speed and yet still be accelerating because your direction is changing.
Neeyik said:What's wrong with asking for something in units that can be appreciated if you're not a scientist? How many people drive through a village and remark that the speed limit is 13.4 m/s?
Well, to begin with I don't see in what every day's life context the gravity acceleration in mph/s is interesting ...
Secondly, I would fully support a 100% transition to the SI system, including road signs in m/s. It just takes a little getting used to. Shouldn't be any harder than switching currency, like all the Euro countries did, which worked out fine. The SI system simply makes so much more sense than everything else out there and is easier to deal with.
Because you don't doesn't mean that other people shouldn't. Ever thought about F1 races where the commentators are saying things like "the drivers are experiencing 5g at this corner". Saying to somebody that their car would need to accelerate in such a way that the speed increases by so many mph every second would help to make it clearer to them.Humus said:
Road signs in metres per second? Just a little getting used to? I started studying physics 17 years ago and I've been teaching it for nearly 8 years, and regardless of the intellect of the student, very few have gained any common sense appreciation of how fast xxx m/s actually is.
The SI system is not based on sense at all - for the most part, it is based on units being forced to accept odd values thanks to piss-poor definitions.
But at least the SI system is base 10 which makes it a little easier to work with than 'old money' systems such as feet, yards and miles! Wasn't a mars probe lost the other year because somebody forgot to change their measurements from imperial to metric or vice-versa?
What would make this even worse is measuring volume. If you had a pint of beer in the US you'd get 17% less than in the UK. Disaster!
What would make this even worse is measuring volume. If you had a pint of beer in the US you'd get 17% less than in the UK. Disaster!
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