HW Assignement 3

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smefix
Beiträge: 83
Registriert: 23.10.2012, 18:54

HW Assignement 3

Beitrag von smefix » 06.11.2016, 15:24

In the attached files you can find the examples from HW 3 and my solutions.
However I cannot guarantee that the solution is 100% correct :)
If anyone finds an error, feel free to tell me :D
Note: I made an typing error while calculating the rotational Energy. I have now uploaded the corrected version :wink:
Du hast keine ausreichende Berechtigung, um die Dateianhänge dieses Beitrags anzusehen.
Zuletzt geändert von smefix am 09.11.2016, 00:12, insgesamt 1-mal geändert.

randomuser
Beiträge: 2
Registriert: 07.11.2016, 16:45

Re: HW Assignement 3

Beitrag von randomuser » 07.11.2016, 17:18

Hey thanks for your solutions - I think you made an error while calculating the center of mass of the wedge. The x2 coordinate should be 2/3 l - you grouped up rho * b * h * l to form the mass of the body, while it actually is 1/2 * rho * b * h * l

regards

Chris
Beiträge: 3
Registriert: 13.10.2016, 14:09

Re: HW Assignement 3

Beitrag von Chris » 08.11.2016, 18:11

I got a different final center of mass vector... I think you did a mistake when calculating the sum.

How do you get a FG=30N? Shouldn't it be 80/3 N? you have a totalmass of 8/3 kg. I not quite sure about it, so maybe you could have a look at yours as well.

regards

smefix
Beiträge: 83
Registriert: 23.10.2012, 18:54

Re: HW Assignement 3

Beitrag von smefix » 08.11.2016, 23:47

randomuser hat geschrieben:Hey thanks for your solutions - I think you made an error while calculating the center of mass of the wedge. The x2 coordinate should be 2/3 l - you grouped up rho * b * h * l to form the mass of the body, while it actually is 1/2 * rho * b * h * l

regards
I calculated the center of mass for the wedge and the bar separately. If you look at page 5 you can see, that I used \frac{\rho \cdot b \cdot h \cdot l}{2} for the wedge. The center of mass should be correct. \frac{2 \cdot l}{3} is only correct if the wedge was rotated by 180°. If you look at the wedge, most of its mass is on the left side.

smefix
Beiträge: 83
Registriert: 23.10.2012, 18:54

Re: HW Assignement 3

Beitrag von smefix » 08.11.2016, 23:52

Chris hat geschrieben:I got a different final center of mass vector... I think you did a mistake when calculating the sum.

How do you get a FG=30N? Shouldn't it be 80/3 N? you have a totalmass of 8/3 kg. I not quite sure about it, so maybe you could have a look at yours as well.

regards
The total mass is \frac{3 \cdot \rho \cdot l \cdot b \cdot h}{2} and \rho=2000 \frac{kg}{m^3}

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