Tire inflation to determine weight

AI Thread Summary
The discussion revolves around calculating the weight of an automobile based on tire inflation pressure and contact area. The correct formula to use is Pfluid = F/A, where the pressure is 1.85E+5 Pa and the contact area per tire is 0.0237 m². After correcting a mathematical error, the weight per tire is determined to be approximately 4384.5 N, leading to a total weight of 17538 N for the four tires combined. Participants emphasize the importance of showing work to identify errors and clarify that each tire supports a fraction of the car's weight. The calculations ultimately confirm the correct approach to solving the problem.
BooGTS
Messages
13
Reaction score
0
Tire inflation to determine weight - solved

The problem goes as follows: he four tires of an automobile are inflated to a gauge pressure of 1.85E+5 Pa. Each tire has an area of 0.0237 m2 in contact with the ground. Determine the weight of the automobile.

But I've applied the Pfluid = F/A and it doesn't seem to pan out. I come up with 447 N per tire, which is wrong.
 
Last edited:
Physics news on Phys.org
Please show your working. It's hard to see where you've gone wrong if you don't show your working.
 
Then you done the arithmetic wrong: 2 x 10^5 times 2x 10^(-2)= 4 x 10^3 or 4000, not 400.
 
I worked on this problem forever before posting and figured it out in this little window on this site of all places. I'm sure it won't be my last tonight though... thanks for the response.

1. 1.85 x10^5 N/m^2 = (x/.0237m^2)

2. 1.85 x10^5 N x .0237 = 4384.5 N = x

3. 4384.5 N x 4 = 17538N =x
 
BooGTS said:
4384.5 N x 4 = 17538N =x

Look's good to me :smile:
 
BooGTS said:
The problem goes as follows: he four tires of an automobile are inflated to a gauge pressure of 1.85E+5 Pa. Each tire has an area of 0.0237 m2 in contact with the ground. Determine the weight of the automobile.

But I've applied the Pfluid = F/A and it doesn't seem to pan out. I come up with 447 N per tire, which is wrong.

As Halls of Ivy said, that looks like a simple mathematical error.

Don't forget each tyre only bears a fraction of the weight of the car. So after getting the force exerted by each tyre on the ground, you need to do something else to find the weight of the car.

EDIT : Ah, OK, you've already posted it, that's correct. :smile:
 
I multiplied the values first without the error limit. Got 19.38. rounded it off to 2 significant figures since the given data has 2 significant figures. So = 19. For error I used the above formula. It comes out about 1.48. Now my question is. Should I write the answer as 19±1.5 (rounding 1.48 to 2 significant figures) OR should I write it as 19±1. So in short, should the error have same number of significant figures as the mean value or should it have the same number of decimal places as...
Thread 'A cylinder connected to a hanging mass'
Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
Back
Top