Updating the suspension of a car

In summary: I don't know... at least in the last (third) group of equations I now think I was calculating the length of a spring of a different length with the same spring constant...I don't know... at least in the last (third) group of equations I now think I was calculating the length of a spring of a different length with the same spring constant...
  • #1
KorvusKoraks
2
0

Homework Statement


A car driver updates the springs of a car by replacing the old springs with stiffer ones. The old springs give an amount of 8 cm when under the car, and their length when not under the car is 29 cm.
The spring constant of the new springs is 30 % greater than that of the old springs.
How long do the new springs have to be in order the car to be located the same distance from the ground with the new springs as with the old springs?

k = the spring constant of the old springs
x = the length of the new spring(s) when under the car
xnorm = the normal ("unloaded") length of the new spring(s)
xreq = the required length of the new spring(s)

Homework Equations


Hooke's law: F = kx

The Attempt at a Solution


I have no idea. I have trouble formulating the equation.

k * (29 cm - 8 cm) = 1.3k * x
k * 21 cm = 1.3k * x || / 1.3k
k * 21 cm / 1.3k = x
x ≈ 16.153 cm

29 cm / 21 cm = xnorm / 16.153 cm
1.381 = xnorm / 16.153 cm || * 16.153 cm
xnorm ≈ 22.307 cm

22.307 cm / 16.153 cm = xreq / 21 cm
1.381 = xreq / 21 cm || * 21 cm
xreq = 29.001 cm ? It's the same as the original!
 
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  • #2
Well, this looks like a beauty contest where I can vote ... :smile:

You can discard the first attempt, because you know for sure that the answer must be more than 21 cm, right ?
Ditto number three, for expectation is less than 29 cm.

Physics isn't a voting contest, though. So the one left standing doesn't have to be the winner.

Can you see what's wrong with your first shot ? What about the x at the end ?
And what about the 8 on the left ? They say 'gives 8 cm' they don't mean it ends up being 8 cm long ...:rolleyes:
 
  • #3
BvU said:
Well, this looks like a beauty contest where I can vote ... :smile:

You can discard the first attempt, because you know for sure that the answer must be more than 21 cm, right ?
Ditto number three, for expectation is less than 29 cm.

Physics isn't a voting contest, though. So the one left standing doesn't have to be the winner.

Can you see what's wrong with your first shot ? What about the x at the end ?
And what about the 8 on the left ? They say 'gives 8 cm' they don't mean it ends up being 8 cm long ...:rolleyes:

I don't know... at least in the last (third) group of equations I now think I was calculating the length of a spring of a different length with the same spring constant...
 
  • #4
KorvusKoraks said:
I don't know... at least in the last (third) group of equations I now think I was calculating the length of a spring of a different length with the same spring constant...
None of the attempts are correct. You need to have a clear idea what each step of the calculation is supposed to be calculating.
In applying equations, you need to be clear what roles the variables play and how those match up to the given data.
In all of the numbers given in the question, which is suitable for use as the 'x' in Hooke's F=kx?
 

FAQ: Updating the suspension of a car

How often should I update the suspension of my car?

The frequency of updating your car's suspension depends on various factors such as the type of roads you drive on, your driving style, and the age and condition of your car. As a general rule, it is recommended to have your suspension checked and serviced every 50,000 miles or every 5 years, whichever comes first. However, if you notice any signs of wear and tear or experience a change in your car's handling, it is best to get it checked by a professional mechanic.

What are the signs that my car's suspension needs to be updated?

There are several signs that indicate your car's suspension may need to be updated. These include excessive bouncing or swaying when driving, uneven tire wear, a bumpy or uncomfortable ride, and difficulty steering or controlling your car. If you notice any of these signs, it is best to have your suspension checked and potentially updated by a professional mechanic.

Can I update my car's suspension myself?

While it is possible to update your car's suspension yourself, it is not recommended unless you have the necessary knowledge, experience, and tools. The suspension is a crucial component of your car's safety and handling, and any mistakes in the update process can have serious consequences. It is best to leave it to a professional mechanic who has the expertise and equipment to properly update your car's suspension.

How long does it take to update a car's suspension?

The time it takes to update a car's suspension depends on the type of update and the condition of the car. In general, a suspension update can take anywhere from a few hours to a full day. This time frame may vary depending on the availability of parts and the complexity of the update. It is best to consult with a professional mechanic to get a more accurate estimate for your specific car and suspension update.

Is updating the suspension of my car expensive?

The cost of updating a car's suspension can vary depending on the type of update and the make and model of the car. In general, a suspension update can cost anywhere from a few hundred dollars to a few thousand dollars. The cost may also depend on the labor rates of the mechanic and the cost of the replacement parts. It is best to get a quote from a professional mechanic before proceeding with the update.

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