Quarter mile 10s car minimum power requirement

[jbriggs444]

Utterly? Now you've got me smiling. This link will take you to a good explanation of mass and weight, including SI and English units and how to calculate mass from weight and vice versa.

Your reference disagrees with you:

"In the EE system 1 lb of force will give a mass of 1 lbm a standard acceleration of 32.17405 ft/s²"

 

[ivtec259]

3,307 lbf (pounds force. Let's call that scale weight) means the object has a mass of 102.7 lbm (pounds mass). That would be about 2.63 slugs, not 102.7 slugs.
3,307 pounds scale weight (lbf) converted to kilograms scale weight would be 1,503 kilograms scale weight (Newtons). Note that Newtons is a force, mass times acceleration. Divide by 9.81(acceleration of Earth's gravity) and you get kilograms mass, about 153.2 kg.

Whaaaaat. No. I think you are the one that needs to check again and then recheck, kind of like in Transformers 1 when that helicopter comes back from the dead.

3,307 pounds scale weight (lbf) is a force. If you want to convert to kilograms, you first need to convert you force into a mass. But fortunately that is easy. It will be 3,307 pounds mass (lbm) on earth. Then you just google 3307 lbm to kg.

 

[OldYat47]

That doesn't disagree with me at all. Note the use of a proportionality constant. Note that 1 lbf is defined as the force that accelerates 1 lbm 32.174 ft/sec^2. Note that gc is defined as (1 lbm)*(32.174*ft/sec^2)/(1 lbf). Note that the slug is still defined as weighing 32.174 pounds.

I'm old enough to have used all these systems in the past. You've had to be very careful, less so today. So I maintain that the car's mass is 102.78 slugs, not 3,307 pounds of anything.

 

[OldYat47]

Picture me slumping in my chair and shaking my head sadly. Suppose you put a weight on a kilogram scale and it weighs 9.81 kg. That's not entirely correct though commonly used. It actually weighs 9.81 Newtons. It has a mass of one kilogram. Refer to the linked site above.

Suppose you take a 2.2 pound weight and put it on the scale above. It will read 1 kilogram. That's it's weight, not it's mass.

Please refer any of this to your local physics instructor.

 

[ivtec259]

That doesn't disagree with me at all. Note the use of a proportionality constant. Note that 1 lbf is defined as the force that accelerates 1 lbm 32.174 ft/sec^2. Note that gc is defined as (1 lbm)*(32.174*ft/sec^2)/(1 lbf). Note that the slug is still defined as weighing 32.174 pounds.

I'm old enough to have used all these systems in the past. You've had to be very careful, less so today. So I maintain that the car's mass is 102.78 slugs, not 3,307 pounds of anything.

Picture me slumping in my chair and shaking my head sadly. Suppose you put a weight on a kilogram scale and it weighs 9.81 kg. That's not entirely correct though commonly used. It actually weighs 9.81 Newtons. It has a mass of one kilogram. Refer to the linked site above.

Suppose you take a 2.2 pound weight and put it on the scale above. It will read 1 kilogram. That's it's weight, not it's mass.

Please refer any of this to your local physics instructor.

Where are they teaching you this? Just curious. Because last I checked with my physics instructor, a kilogram is a unit of mass and nothing else. If you want to talk about forces, then talk Newton. And how can you believe that I meant a force, when I wrote m = 1500 kg. I did not write F = 1500 kgf.

You can maintain what you want, but in the USA I know they use pounds mass (lbm) for measuring the mass of most things, including cars.

 

[OldYat47]

You will be shocked if you travel outside this country to discover that things like flour, rice, coffee and dozens of other commodities are sold by the kilogram or gram weight. Even cars are quoted as weighing a number of kilograms. It's sloppy, but there you go. So take my post above to your physics instructor and see what he or she says about it. You can find scales with Newton readouts, but the vast majority are in grams and kilograms weight, not mass.

Lastly, and repeating myself, a car that weighs 3,307 pounds has a mass of about 153 kg.
Moderator note: The sentence above is patently untrue. An object whose mass is 153 kg would have a weight of about 336.6 lb.

I have to leave for today, but tomorrow I will work on the numbers presented above as solutions for t1, t2, etc.

 

[ivtec259]

You will be shocked if you travel outside this country to discover that things like flour, rice, coffee and dozens of other commodities are sold by the kilogram or gram weight. Even cars are quoted as weighing a number of kilograms. It's sloppy, but there you go. So take my post above to your physics instructor and see what he or she says about it. You can find scales with Newton readouts, but the vast majority are in grams and kilograms weight, not mass.

Oh so you mean that saying for example that "My car weighs 1500 kg" is wrong and you should say "My car's mass is 1500kg"? And by the way, I do not live in the US.

 

[berkeman]

Thread closed for Moderation...

 

[berkeman]

This thread will remain closed. You guys sound like a couple of 10 year olds arguing over marbles. This will not be tolerated at the PF. Please don't post with this kind of attitude here again. Fair warning.