Find spring constant of spring in N/m.help

In summary, the spring constant can be calculated using Hooke's law, which states that the force exerted by a spring is equal to the spring constant multiplied by the displacement from equilibrium. In the first conversation, the correct spring constant was found by using the formula k = mg/x. In the second conversation, the energy stored in a spring was found using the formula E = 1/2 kx^2. The spring constant also depends on factors such as the material of the spring and its geometry. In the third conversation, the height of the popper when stretched is not the same as the compressed height. In the fourth conversation, the spring constant was used to calculate the elastic potential energy stored in the spring.
  • #1
Cougar1112
9
0
A mass of 100 g causes a vertical spring to stretch by 2.0 cm. a) find the spring constant of the spring in N/m: No picture was given to me.

Ok I am not sure if this is the formula to find spring constant so is it:

k= mg/x

and if so the answer is

k=(100)(9.81)/2.0 cm
k= 490.5 N/m

is this correct?
 
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  • #2
The formula (Hooke's law) is correct. But check your units. I recommend that you convert all quantities to standard units before plugging numbers into the formula. (What are the standard units for length and mass?)
 
  • #3
Ok here is the correct solution.

k=mg/x

k= (.1kg)(9.81)/.02m
k= 49.1 N/m

so I got the correct answer by using hooke's law?

Now that I got that then for part b it asks:

How much force wil cause the spring to compress by 0.5 cm?

F=-kx

So the answer is

F= (-49.1N/m)(.005m)= -.25 N

Did I do it right?
 
  • #4
Cougar1112 said:
Ok here is the correct solution.

k=mg/x

k= (.1kg)(9.81)/.02m
k= 49.1 N/m

so I got the correct answer by using hooke's law?
Good.

Now that I got that then for part b it asks:

How much force wil cause the spring to compress by 0.5 cm?

F=-kx

So the answer is

F= (-49.1N/m)(.005m)= -.25 N

Did I do it right?
Yes, except for that minus sign. Just give the magnitude of the force. (The meaning of the minus sign in Hooke's law is just that the force exerted by the spring is opposite to the displacement from equilibrium. If you pull the spring to the right, the spring force pulls back to the left. Don't get hung up on this.)
 
  • #5
Thanks Doc. I might be back shortly if I have any more problems.
 
  • #6
similar question:

What is the spring constant of a spring that stores 25 J of elastic potential energy when compressed by 6.0 cm from its relaxed length?


I've tried using N*m = J (work) to find my Newtons and dividing by the distance:

N*0.06m = 25J
N = 25 / 0.06
N = 416.667

N/m = 416.667N / 0.06m
N/m = 6944.444

for some reason, that's wrong. I'm wondering if perhaps the sign matters?
 
  • #7
Energy stored in a spring

tbomber said:
I've tried using N*m = J (work) to find my Newtons and dividing by the distance:
I assume you mean Work = Force x distance. That only works if the force is constant, but that's not true here. The more the spring is compressed, the stronger it pushes back. Either integrate ([itex]dW = F(x) dx[/itex]) or look up the formula for the energy stored in a compressed spring.
 
  • #8
ah, found it! thanks for the help Doc
 
  • #9
The force required to stretch a Hooke’s-law spring varies from 0 N to 52.4 N as we stretch the spring by moving one end 13.8 cm from its unstressed position. Find the force constant of the spring. Answer in units of N/m.

Cant i just Take

Force final = -k(change in x)
 
  • #10
Hi, so what if the spring isn't vertical? I have the mass, displacement, and frequency of the spring and I'm being asked to find the acceleration. Do I need to find the spring constant in order to do that?
 
  • #11
on what factors spring constant depends?
for example if we attatch mass to a particular spring and calculate frequency, then we cut the spring into two halves and attatch the same mass to one of the halves. is there any difference in frequency or not then?
please help me out.
 
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  • #12
so I am doing a real life situation lab. but with poppers. (you know the little rubber ones you put inside out and let pop up and you go AH!). and all I am asking is the x. when it's "Stretch like in the original problem asked in this thread would that be the hight compressed (i don't think so since it's 'compressed') the average height? I am guessing the average height
 
  • #13
Hi I need help in one of these exam questions from the AQA Physics a level exam in springs constant.Unit 02 - Mechanics, Materials and Waves Question Paper on question 1aiii)

http://www.aqa.org.uk/qualifications/a-level/science/physics-a/physics-a-key-materials [Broken]

PLEASE HELPP!
 
Last edited by a moderator:
  • #14
A teddy bear of mass 400 grams is hung from the end of a spring. The spring measures 51.0cm long in the rest position; when the teddy bear is attached to the end of the spring, the spring extends to 72.0cm. Calculate the elastic potential energy stored in the spring when extended to 72.0cm.
 

1. How do I find the spring constant of a spring in N/m?

The spring constant, also known as the force constant, is a measure of how stiff a spring is and is represented by the letter k. It is typically measured in Newtons per meter (N/m). To find the spring constant, you will need to know the force applied to the spring and the displacement of the spring from its original position. Then, you can use the equation k = F/x, where k is the spring constant, F is the force applied, and x is the displacement.

2. Can I use a ruler to measure the displacement of the spring?

Yes, you can use a ruler to measure the displacement of the spring. Make sure the ruler is placed next to the spring and measure the distance between the starting point and the end point of the spring after the force is applied. This will give you the displacement value (x) needed to calculate the spring constant.

3. What units should I use when measuring the force and displacement?

The force should be measured in Newtons (N) and the displacement should be measured in meters (m) in order to get the spring constant in N/m. If you are using different units, you can convert them using appropriate conversion factors.

4. Can I use this method to find the spring constant for any type of spring?

Yes, you can use this method to find the spring constant for any type of spring as long as the spring follows Hooke's Law, which states that the force exerted by a spring is directly proportional to the displacement of the spring from its original position. This means that the spring will have a constant spring constant throughout its range of motion.

5. What are some factors that may affect the accuracy of my calculated spring constant?

Some factors that may affect the accuracy of your calculated spring constant include the precision of your measurements, the condition of the spring, and external forces such as air resistance. It is important to ensure that your measurements are as accurate as possible to get an accurate spring constant value.

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