Finding little g using an inclined plane

In summary: Yes, air resistance and rolling resistance will lead to underestimates. Other errors, like timing offset and granularity, could go either way.Might be a good idea to have three photo timers (I forget the technical term) so you don't have to worry about starting from rest.
  • #1
Ahmed Mutaz
5
0
Homework Statement
Is it possible to find the value of g by rolling a wheel (I=mr^2) down an incline and plotting v^2 vs h(vertical length of the incline) by varying the angle? Assuming you can find the final velocity? I think it might work because mgh=0.5mv^2+0.5Iw^2 gives v^2=gh
Relevant Equations
Energy Conservation with rolling without slipping
The slope of the v^2 vs h graph is g
 
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  • #2
Ahmed Mutaz said:
mgh=0.5mv^2+0.5Iw^2 gives v^2=gh
Not quite. What is I in this case?
 
  • #3
haruspex said:
Not quite. What is I in this case?
I=mr^2
 
  • #4
Ahmed Mutaz said:
I=mr^2
Ah, sorry, didn't notice you specified that. But you would never quite achieve it. Better to specify a uniform disc.
 
  • #5
haruspex said:
Ah, sorry, didn't notice you specified that. But you would never quite achieve it. Better to specify a uniform disc.
I meant a hoop/wheel thing idk how to describe it but it has a moment of inertia of I=mr^2. So assuming that is true, would you be able to obtain a value close to 9.8 for g?
 
  • #6
Ahmed Mutaz said:
I meant a hoop/wheel thing idk how to describe it but it has a moment of inertia of I=mr^2. So assuming that is true, would you be able to obtain a value close to 9.8 for g?
I understand, but to be literally mr2 it would have to be very thin radially, so could easily get bent out of round. I'm just saying it would be easier to arrange for a uniform disc.
 
  • #7
haruspex said:
I understand, but to be literally mr2 it would have to be very thin radially, so could easily get bent out of round. I'm just saying it would be easier to arrange for a uniform disc.
I figured as much; I’m only saying that assuming we have a shape that can be approximated to mr^2 does plotting v^2 against h give a decent value of g? I don’t really see any other problems besides the mr^2 approximation so forget about it for now. Also, I believe it is possible to get really thin hoops.
 
  • #8
Ahmed Mutaz said:
I figured as much; I’m only saying that assuming we have a shape that can be approximated to mr^2 does plotting v^2 against h give a decent value of g? I don’t really see any other problems besides the mr^2 approximation so forget about it for now. Also, I believe it is possible to get really thin hoops.
Yes, the principle is fine.
 
  • #9
haruspex said:
Yes, the principle is fine.

Thanks for confirming the theory. Now another hypothetical, last question lol, because of air resistance wouldn’t you get an under approximation of g? Or do you think there are other sources of error that may cause it to be an overestimation?
 
  • #10
Ahmed Mutaz said:
Thanks for confirming the theory. Now another hypothetical, last question lol, because of air resistance wouldn’t you get an under approximation of g? Or do you think there are other sources of error that may cause it to be an overestimation?
Yes, air resistance and rolling resistance will lead to underestimates. Other errors, like timing offset and granularity, could go either way.
Might be a good idea to have three photo timers (I forget the technical term) so you don't have to worry about starting from rest.
 

Related to Finding little g using an inclined plane

1. How does an inclined plane help find little g?

An inclined plane is a simple machine that allows for the measurement of the force needed to move an object up or down a slope. By using an inclined plane, the force needed to move an object can be compared to the force of gravity acting on the object, which can then be used to calculate the acceleration due to gravity (little g).

2. What materials are needed to conduct an inclined plane experiment?

To conduct an inclined plane experiment to find little g, you will need an inclined plane (such as a ramp or a board propped up on one end), a small object (such as a toy car or ball), a measuring tape or ruler, and a stopwatch or timer.

3. How do you calculate little g using an inclined plane?

To calculate little g using an inclined plane, you will need to measure the length of the inclined plane (L), the height of the inclined plane (h), and the time it takes for the object to roll down the inclined plane (t). Then, you can use the formula g = 2h/t^2 to calculate the acceleration due to gravity.

4. What are some sources of error in an inclined plane experiment?

Some sources of error in an inclined plane experiment include friction between the object and the inclined plane, air resistance, and human error in measuring the length and height of the inclined plane or the time it takes for the object to roll down.

5. Why is it important to find little g using an inclined plane?

Finding little g using an inclined plane is important because it allows for the measurement of the acceleration due to gravity in a controlled and repeatable experiment. This value is a fundamental constant in physics and is used in various calculations and equations, making it crucial to accurately determine.

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