Gravitational attraction of plumbline

[TimSon]

Homework Statement

By what angle, in seconds of arc, will a plumbline be pulled out of its normal vertical direction by the gravitation attraction of a 10-ton that parks 20 ft away? Do you think that this effect could be detected?

Homework Equations

I think (G*m1*m2)/r^2

The Attempt at a Solution

[/B]
I first converted 10 tons to Newtons which i got to be around 88964 Newtons (from some conversion website).

then i divided 88964 by 9.8 to get 9077.96 kg for the truck.

20 ft becomes 6.096 meters.

Plugging this into the equation, I get

(G * (m(plumb) * 9077.96 kg))/(6.096 m)^2

I don't know how to find the mass of the plumbline.

 

[BvU]

Hi TS,

Converting tons to new tons (sorry) isn't working properly. Dimensions don't match. In my region (I presume SI, but the ton doesn't fit in there) 1 ton is 1000 kg. What about your tons? Are they tonnes or tons (long, short, UK, US, himalaya, etc... -- only you can tell) ?

And you don't need the mass of the plumb. Write out a few equations that help you find the angle they are asking for. Who knows this mass might divide out...

 

[Chestermiller]

The title of this thread does not conform to PF rules and guidelines. Please provide a new title.

Chet

 

[BvU]

Chet is right of course. Except for that and my advice in post #2, yet another tip: make a drawing! Or even two: one free body diagram for a plumb (i.e. ⊥) plumb and one where the plumb is attracted towards a parked truck. Exaggerate the angle () and then work out the post#2 tip.

[edit] and I wonder why you do worry about the mass of the plumbline, but not about its length !? Or am I making it worse now?)

 

[Mark44]

The title of this thread does not conform to PF rules and guidelines. Please provide a new title.

Fixed.

 

[TimSon]

Fixed.

Thanks I did not know how to change the name of the thread. (I still don't despite attempting to look for the answer).

 

[TimSon]

Chet is right of course. Except for that and my advice in post #2, yet another tip: make a drawing! Or even two: one free body diagram for a plumb (i.e. ⊥) plumb and one where the plumb is attracted towards a parked truck. Exaggerate the angle () and then work out the post#2 tip.

[edit] and I wonder why you do worry about the mass of the plumbline, but not about its length !? Or am I making it worse now?)

Thanks for all the help BvU.

I have been trying to model this like a pendulum, however I have been trying for sometime and it seems that I am doing something wrong.

Is this the right approach or is this completely wrong?

Furthermore, my thinking is that the Tension in the X direction (back towards the vertical) would be equal to the Force of Gravity from the truck.

Thanks,

 

[BvU]

I have been trying to model this like a pendulum

A swinging plumb is no good . Better look at the equilibrium situation. Easier.

Furthermore, my thinking is that the Tension in the X direction (back towards the vertical) would be equal to the Force of Gravity from the truck

looks good to me. Tension is force. Force is mass times acceleration. Plumb mass is the same in both cases-- that's why it cancels. Is that enough of a "hint" ?

Can you post your free body diagram ?

 

[TimSon]

Here is a handdrawn version. I hope you can read it, but if not, please tell me. I then proceeded to have Tx = Fg. Thanks for the help
.