## HW Assignement 3

smefix
Beiträge: 83
Registriert: 23.10.2012, 18:54

### HW Assignement 3

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
Note: I made an typing error while calculating the rotational Energy. I have now uploaded the corrected version
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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

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

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

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

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 $\rho=2000 \frac{kg}{m^3}$