Calculating Error in Horizontal Velocity for Bouncing Ball Experiment

  • Thread starter Thread starter physicssss
  • Start date Start date
  • Tags Tags
    Error Propagation
AI Thread Summary
The discussion focuses on calculating the error in horizontal velocity for a bouncing ball experiment. The equation for horizontal velocity is given, and participants analyze various options for expressing the error in this velocity. There is some confusion regarding the factor of 2 in the height variable, with one participant suggesting it may affect the choice of the correct error equation. However, it's clarified that the factor of 2 is simply a constant and does not change the fundamental relationship of the variables involved. The key takeaway is that understanding the powers of the variables is crucial for determining the correct error expression.
physicssss
Messages
9
Reaction score
0

Homework Statement


I slide a ball off of a ramp (the ramp is on a table) and the ball hits the ground and bounces horizontally and vertical.
I know that horizontal velocity = horizontal distance*sqrt(gravity/2*height) or d*sqrt(g/2h)
I want to know the equation for calculation error.

The expression for the error in the horizontal component of ball's velocity is:
Select one:
a. error v = v[(error d)/d + (error g)/g +(error h)/h]
b. error v/2 = v[(error d)/d + (error g)/g +(error h)/h]
c. error v/4 = v[(error d)/d + (error g)/g +(error 2h)/h]
d. error v = v[(error d)/d + (error g)/g +(error 2h)/h]
e. error v/2 = v[(error 2d)/d + (error g)/g +(error h)/h]


Homework Equations





The Attempt at a Solution


I think its a. The problem I have is the 2h. I don't know how to deal with it. If v=sqrt(g/h) then I know for sure the answer is a. but since that 2 is there I don't know if the answer is still a.
 
Physics news on Phys.org
If x is a function of measured variables u, v, \ldots,
x = f(u, v, \ldots),
then,
\sigma_x^2 \approx \sigma_u^2 \left ( \frac{\partial x}{\partial u}<br /> \right )^2 + \sigma_v^2 \left ( \frac{\partial x}{\partial v} \right )^2<br /> + \ldots \;.
You should be able to figure it out from there. Except that I think you may have written down the possible solutions incorrectly; aren't there some missing square roots?
 
None of the choices seem right to me.
Don't worry about the 2 in the 2h. That's just a factor of root 2 on the whole expression. It has no relationship to the h specifically. What matters is the powers of the variables. If e.g. z = A xmyn then Δz/z = m Δx/x + n Δy/y. It's just the normal product rule of differentiation.
 
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