Relationship between centripetal force and radius

In summary, the conversation is about a physics lab where the relationship between centripetal force and radius is being studied. A constant centripetal force of 2N is used and the frequency in RPM is recorded for different radii. The next step is to plot a graph of Fc versus frequency squared, with the instruction to draw a line from each point to the origin. The question is whether to simply square the frequency or if there is a trick to understand. It is suggested that the next step would be to try to find a relationship between the angular frequency or angular frequency squared and the radii, and to compute Fc/frequency^2 for each point and graph those values versus the radii. The expected outcome is
  • #1
kiss89
13
0
hi I'm a new member in this forum and I'm taking physics(University level) grade 12...in one of our labs about the relationship between centripetal force and radius, we must use a constant centripetal force( we used 2N) and find the frequency in RPM for different radii, and this is what we got:
Fc:2N ( Constant)
Radius: RPM:
0.8 88
0.6 113
0.4 138
0.2 192
then he asked to plot a graph of Fc versus frequency squared.
(Note:also it says after that to draw a line from each point to the origin because Fc for frequency 0Hz is 0)
my question is do we just square the frequency we got in experiment, or is there some kind of a trick he wants us to understand?
If u could explain this to me please, i'd be very grateful.
THANK YOU.
 
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  • #2
kiss89 said:
hi I'm a new member in this forum and I'm taking physics(University level) grade 12...in one of our labs about the relationship between centripetal force and radius, we must use a constant centripetal force( we used 2N) and find the frequency in RPM for different radii, and this is what we got:
Fc:2N ( Constant)
Radius: RPM:
0.8 88
0.6 113
0.4 138
0.2 192
then he asked to plot a graph of Fc versus frequency squared.
(Note:also it says after that to draw a line from each point to the origin because Fc for frequency 0Hz is 0)
my question is do we just square the frequency we got in experiment, or is there some kind of a trick he wants us to understand?
If u could explain this to me please, i'd be very grateful.
THANK YOU.
Are you certain you are supposed to be plotting Fc versus frequency squared? Since you held Fc constant and varied r and frequency, it would seem more reasonable to be plotting r vs frequency (or maybe 1/r or 1/r^2 since r is decreasing as the frequency increases). Maybe you were asked to try some different graphs, drawing the best straight line you can from the orign through the data points?
 
  • #3
well in this lab we had to spin a string with mass ( which is constant 20 g) attached to its end above us and this is what it says in the lab:

In this part of the experiment, we will calculate the centripetal force and the radius of the circle with frequency as the constant.

1) Adjust the string to provide a radius of rotation of 0.8m
2) Swing the rubber stopper in a horizontal circle keeping the scale reading constant at 2N or 200g
3) Record the number of rotations and time in a data table. Calculate the frequency and frequency squared and record these numbers in your data table.
4) Repeat steps 1 to 3 for radii of 0.8m, 0.6m, 0.4 m, 0.2 m
 
  • #4
can anybody help me with this pleasez
 
  • #5
does anyone have any idea please, my due date is getting closer
 
  • #6
kiss89 said:
well in this lab we had to spin a string with mass ( which is constant 20 g) attached to its end above us and this is what it says in the lab:

In this part of the experiment, we will calculate the centripetal force and the radius of the circle with frequency as the constant.

1) Adjust the string to provide a radius of rotation of 0.8m
2) Swing the rubber stopper in a horizontal circle keeping the scale reading constant at 2N or 200g
3) Record the number of rotations and time in a data table. Calculate the frequency and frequency squared and record these numbers in your data table.
4) Repeat steps 1 to 3 for radii of 0.8m, 0.6m, 0.4 m, 0.2 m
All of that makes sense. The next logical step is to try to find a relationship between the angular frequency or angular frequency squared (there is probably a reason they asked you to calculate that) and the radii.

If you do the graph you said you were asked to draw, all the points will have the same value for Fc. The only reason for drawing a line from each point to the origin is that you will see a set of lines with different slopes. The slopes of these lines are probably what your teacher wants you to compute. (You don't need a graph for this, but let's not worry about that.) If you compute Fc/frequency^2 for each point, do you see any connection between those values and the radii? If you don't see a connection, I suggest you make a graph of those computed values vs the radii. What kind of curve can you draw that goes through or near all the points on that graph?
 
  • #7
i don't know if I'm right , but the computed values i got from Fc/Freq.^2 are the same as the radii , and i got a line where it almost passes through 3 points out of 4 , and the last point is far away from the line , as in the picture attached
 

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  • #8
i don't know if I'm right , but the computed values i got from Fc/Freq.^2 are the same as the radii , and i got a line where it almost passes through 3 points out of 4 , and the last point is far away from the line , as in the picture attached
 
  • #9
kiss89 said:
i don't know if I'm right , but the computed values i got from Fc/Freq.^2 are the same as the radii , and i got a line where it almost passes through 3 points out of 4 , and the last point is far away from the line , as in the picture attached
I won't be able to see your graph for a while, but theoretically it should be a straight line through the origin, showing that the centripetal force divided by angular frequency squared is directly proportional to the radius of the circle. If you use the frequency and the circumference of the circle to figure out how fast the object was moving, you could rearrange terms to show that the centripetal force is the mass of the object times its speed squared divided by the radius.
 
  • #10
ok thanks for your help i think i understood what he wants
 

FAQ: Relationship between centripetal force and radius

1. What is centripetal force?

Centripetal force is a force that acts towards the center of a circular motion, keeping an object moving along a circular path.

2. How is centripetal force related to radius?

The centripetal force is directly proportional to the radius of the circular path. This means that as the radius increases, the centripetal force also increases.

3. What is the formula for calculating centripetal force?

The formula for centripetal force is F = (mv^2)/r, where m is the mass of the object, v is the velocity, and r is the radius of the circular path.

4. How does changing the radius affect the centripetal force?

As mentioned earlier, increasing the radius will increase the centripetal force needed to keep the object moving along the circular path. Conversely, decreasing the radius will decrease the required centripetal force.

5. What are some real-world applications of the relationship between centripetal force and radius?

The relationship between centripetal force and radius is important in many real-world scenarios, such as understanding the forces acting on a car while turning, designing roller coasters and other amusement park rides, and calculating the orbit of planets and satellites in space.

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