## Simple Machines B/Compound Machines C

Unome
Moderator
Posts: 4250
Joined: January 26th, 2014, 12:48 pm
State: GA
Location: somewhere in the sciolyverse
Has thanked: 64 times
Been thanked: 29 times

### Re: Simple Machines B/Compound Machines C

plaid suit guy2 wrote:What you're saying sounds like it does this.
Ohh... I should have mentioned which parts were stationary... I intended for both the gears to remain stationary.
Userpage
Chattahoochee High School Class of 2018
Georgia Tech Class of 2022

Opinions expressed on this site are not official; the only place for official rules changes and FAQs is soinc.org.

plaid suit guy2
Member
Posts: 60
Joined: May 19th, 2013, 6:45 pm
Division: C
State: CO
Has thanked: 0
Been thanked: 0

### Re: Simple Machines B/Compound Machines C

Okay, so if both gears are stationary, then the big circle will be the 1.5m radius of the eccentric (I have no idea where 1.65 came from). The little circle will be the 2m radius of the dot from the center of it's shaft. Even if the two circles are the same size, it will always do this unless they are coaxial.
blue and yellow plaid suit
Nationals 2012:
Sound of Music: 8th

Nationals 2013:
Remote Sensing: 1st
ELG: 1st
MagLev: 6th

State 2014:
Boomi: 1st (scored 1824)
Circuits: 1st
Compound: 3rd
Malgev: 1st
MP: 2nd

total gold: 18
total silver: 10
total bronze: 5
6th: 1
Poudre High School class of '15

plaid suit guy2
Member
Posts: 60
Joined: May 19th, 2013, 6:45 pm
Division: C
State: CO
Has thanked: 0
Been thanked: 0

### Re: Simple Machines B/Compound Machines C

Double posting, but you are right, it isn't an eccentric, but you are wrong about the radii. The radius of the swing must be added to the radius of the second wheel. Meaning the radius would be seen as 2.5m if the swing is .5m. Yielding .6*5π=9.42m

Okay now that that is done: I have two problems.
The first: The easiest question on the Colorado State Comp-comp test:
Ignore friction. This lever is in static equilibrium with a force Fp applied by the piston at a 30° angle θ to the bar, what is the force applied to the fulcrum Φ?
divCstate.png (11.15 KiB) Viewed 2172 times
The second is more a div B level question. What is the load mass to maintain static equilibrium on the lever? (this is so much lower in quality, sorry)
Div.b lever.png (7.91 KiB) Viewed 2172 times
blue and yellow plaid suit
Nationals 2012:
Sound of Music: 8th

Nationals 2013:
Remote Sensing: 1st
ELG: 1st
MagLev: 6th

State 2014:
Boomi: 1st (scored 1824)
Circuits: 1st
Compound: 3rd
Malgev: 1st
MP: 2nd

total gold: 18
total silver: 10
total bronze: 5
6th: 1
Poudre High School class of '15

UTF-8 U+6211 U+662F
Exalted Member
Posts: 1523
Joined: January 18th, 2015, 7:42 am
Division: C
State: PA
Has thanked: 0
Been thanked: 1 time

### Re: Simple Machines B/Compound Machines C

plaid suit guy2 wrote:Double posting, but you are right, it isn't an eccentric, but you are wrong about the radii. The radius of the swing must be added to the radius of the second wheel. Meaning the radius would be seen as 2.5m if the swing is .5m. Yielding .6*5π=9.42m

Okay now that that is done: I have two problems.
The first: The easiest question on the Colorado State Comp-comp test:
Ignore friction. This lever is in static equilibrium with a force Fp applied by the piston at a 30° angle θ to the bar, what is the force applied to the fulcrum Φ?
Pulley: $\text{IMA} = 4$
$20N/4 = 5N$
$5N * 15 = 75N$
$90 - 30 = 60$
$cos(60) * F_p = \frac{F_p}{2}$
$\frac{F_p}{2} * 5 = \frac{5F_p}{2}$
$F_\phi = 75N - \frac{5F_p}{2} \text{upwards}$

plaid suit guy2
Member
Posts: 60
Joined: May 19th, 2013, 6:45 pm
Division: C
State: CO
Has thanked: 0
Been thanked: 0

### Re: Simple Machines B/Compound Machines C

This is incorrect, Fp can be found, for one thing.
blue and yellow plaid suit
Nationals 2012:
Sound of Music: 8th

Nationals 2013:
Remote Sensing: 1st
ELG: 1st
MagLev: 6th

State 2014:
Boomi: 1st (scored 1824)
Circuits: 1st
Compound: 3rd
Malgev: 1st
MP: 2nd

total gold: 18
total silver: 10
total bronze: 5
6th: 1
Poudre High School class of '15

UTF-8 U+6211 U+662F
Exalted Member
Posts: 1523
Joined: January 18th, 2015, 7:42 am
Division: C
State: PA
Has thanked: 0
Been thanked: 1 time

### Re: Simple Machines B/Compound Machines C

plaid suit guy2 wrote:This is incorrect, Fp can be found, for one thing.
There are two variables though... (and only one equation).

Unless I'm making some stupid mistake (still a little tired after States)

plaid suit guy2
Member
Posts: 60
Joined: May 19th, 2013, 6:45 pm
Division: C
State: CO
Has thanked: 0
Been thanked: 0

### Re: Simple Machines B/Compound Machines C

There are three equations, each with only one variable
blue and yellow plaid suit
Nationals 2012:
Sound of Music: 8th

Nationals 2013:
Remote Sensing: 1st
ELG: 1st
MagLev: 6th

State 2014:
Boomi: 1st (scored 1824)
Circuits: 1st
Compound: 3rd
Malgev: 1st
MP: 2nd

total gold: 18
total silver: 10
total bronze: 5
6th: 1
Poudre High School class of '15

UTF-8 U+6211 U+662F
Exalted Member
Posts: 1523
Joined: January 18th, 2015, 7:42 am
Division: C
State: PA
Has thanked: 0
Been thanked: 1 time

### Re: Simple Machines B/Compound Machines C

plaid suit guy2 wrote:There are three equations, each with only one variable
I just give up.

plaid suit guy2
Member
Posts: 60
Joined: May 19th, 2013, 6:45 pm
Division: C
State: CO
Has thanked: 0
Been thanked: 0

### Re: Simple Machines B/Compound Machines C

You sure?
The first problem is this
Try the second question.
blue and yellow plaid suit
Nationals 2012:
Sound of Music: 8th

Nationals 2013:
Remote Sensing: 1st
ELG: 1st
MagLev: 6th

State 2014:
Boomi: 1st (scored 1824)
Circuits: 1st
Compound: 3rd
Malgev: 1st
MP: 2nd

total gold: 18
total silver: 10
total bronze: 5
6th: 1
Poudre High School class of '15

UTF-8 U+6211 U+662F
Exalted Member
Posts: 1523
Joined: January 18th, 2015, 7:42 am
Division: C
State: PA
Has thanked: 0
Been thanked: 1 time

### Re: Simple Machines B/Compound Machines C

plaid suit guy2 wrote:You sure?
The first problem is this
Now I get it. I forgot the $\Sigma F = 0$ part...
4 kg