## Machines B/C

AwersomeUser
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Posts: 116
Joined: December 8th, 2018, 5:20 am
Division: B

### Re: Machines B/C

Ah! Sorry, I forgot to hide my answer...

1) Most machines have an actual mechanical advantage of more less one. True/False
2) The following is an example of what kind of simple machines?

3) A boy and a girl each sits on one end of a seesaw. When the 120 kg girl sits down, the boy rises/goes up by 0.4 m; when the boy sits down, the girl rise/goes up by 20 cm. How heavy is the boy in kilogram?
(Hope the wording isn’t too confusing)
I'll take a stab at it... 1) Most have more than one AMA
2) Belt and Pulley, or just 2 pulleys
3) 60KG? I'm more than a bit confused on this question, is this even possible?
Correct for one. I wouldn’t put belt too for two. The correct answer for 3 is 9.6 kg. I guess the
problem doesn’t make sense with a boy that weights 9.6 kg. (Ugh... If someone’s 9.6 kg they are probably still a baby/toddler, not a boy...) I was going to make him weigh 96 kg... How did you get 60 kg? Maybe I am wrong.

JoeyC
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Posts: 252
Joined: November 7th, 2017, 1:43 pm
Division: C
State: TX

### Re: Machines B/C

How did you get the answer in the first place? As far as I see the system would just oscillate until it stopped due to frictional forces... (I mean, not just from a physics standpoint, it's called a seesaw because when you get on it it goes up and down)
Ohayo!
`Dynamic Planet, Protein Modeling, Fast Facts, Thermodynamics`
`Dynamic Planet, Compound Machines, Chem Lab, WaQua (maybe), Ornith (maybe)`
1 Corinthians 13:4-7
Scientia Potentia Est

UTF-8 U+6211 U+662F
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Posts: 1518
Joined: January 18th, 2015, 7:42 am
Division: C
State: PA

### Re: Machines B/C

Ah! Sorry, I forgot to hide my answer...

1) Most machines have an actual mechanical advantage of more less one. True/False
2) The following is an example of what kind of simple machines?

3) A boy and a girl each sits on one end of a seesaw. When the 120 kg girl sits down, the boy rises/goes up by 0.4 m; when the boy sits down, the girl rise/goes up by 20 cm. How heavy is the boy in kilogram?
(Hope the wording isn’t too confusing)
I'll take a stab at it... 1) Most have more than one AMA
2) Belt and Pulley, or just 2 pulleys
3) 60KG? I'm more than a bit confused on this question, is this even possible?
Correct for one. I wouldn’t put belt too for two. The correct answer for 3 is 9.6 kg. I guess the
problem doesn’t make sense with a boy that weights 9.6 kg. (Ugh... If someone’s 9.6 kg they are probably still a baby/toddler, not a boy...) I was going to make him weigh 96 kg... How did you get 60 kg? Maybe I am wrong.
A boy weighing 96 kg would be rather concerning since average American adult males weigh around 90 kg.

AlfWeg
Member
Posts: 89
Joined: July 22nd, 2019, 7:52 am
Division: C
State: MI

### Re: Machines B/C

Ah! Sorry, I forgot to hide my answer...

1) Most machines have an actual mechanical advantage of more less one. True/False
2) The following is an example of what kind of simple machines?

3) A boy and a girl each sits on one end of a seesaw. When the 120 kg girl sits down, the boy rises/goes up by 0.4 m; when the boy sits down, the girl rise/goes up by 20 cm. How heavy is the boy in kilogram?
(Hope the wording isn’t too confusing)
I'll take a stab at it... 1) Most have more than one AMA
2) Belt and Pulley, or just 2 pulleys
3) 60KG? I'm more than a bit confused on this question, is this even possible?
Correct for one. I wouldn’t put belt too for two. The correct answer for 3 is 9.6 kg. I guess the
problem doesn’t make sense with a boy that weights 9.6 kg. (Ugh... If someone’s 9.6 kg they are probably still a baby/toddler, not a boy...) I was going to make him weigh 96 kg... How did you get 60 kg? Maybe I am wrong.
Would u mind explaining number 3? I always thought that was not possible...
Last&SeventhYearOlympian
```NorView/CenterVille/UMICH/r/s:
Machines: 2/
DP: 1/
Code:X/
GeoMap:X/
Protein: 2/
```
It's kinda Dull -->AlfWeg's Userpage

knightmoves
Member
Posts: 202
Joined: April 26th, 2018, 6:40 pm

### Re: Machines B/C

Would u mind explaining number 3? I always thought that was not possible...
Yeah - that's not how seesaws work. If a boy and a girl sit on a seesaw, the heavier one falls down until his or her legs stop the motion. The height of the lighter one depends on the leg extension of the heavier one, and not on their relative weights.

AlfWeg
Member
Posts: 89
Joined: July 22nd, 2019, 7:52 am
Division: C
State: MI

### Re: Machines B/C

Would u mind explaining number 3? I always thought that was not possible...
Yeah - that's not how seesaws work. If a boy and a girl sit on a seesaw, the heavier one falls down until his or her legs stop the motion. The height of the lighter one depends on the leg extension of the heavier one, and not on their relative weights.
Oh goodie I’m not crazy. But I’m just wondering how the Awersome got an answer. Maybe he meant length?
Last&SeventhYearOlympian
```NorView/CenterVille/UMICH/r/s:
Machines: 2/
DP: 1/
Code:X/
GeoMap:X/
Protein: 2/
```
It's kinda Dull -->AlfWeg's Userpage

AwersomeUser
Member
Posts: 116
Joined: December 8th, 2018, 5:20 am
Division: B

### Re: Machines B/C

Would u mind explaining number 3? I always thought that was not possible...
Yeah - that's not how seesaws work. If a boy and a girl sit on a seesaw, the heavier one falls down until his or her legs stop the motion. The height of the lighter one depends on the leg extension of the heavier one, and not on their relative weights.
Yes, probably. Pretend I never posted that question.

AlfWeg
Member
Posts: 89
Joined: July 22nd, 2019, 7:52 am
Division: C
State: MI

### Re: Machines B/C

Lol I make mistakes like that all the time

A 20 kg block is stationary on a inclined plane(20 degree angle). What is the coefficient of static friction? Use g= 9.81
Last&SeventhYearOlympian
```NorView/CenterVille/UMICH/r/s:
Machines: 2/
DP: 1/
Code:X/
GeoMap:X/
Protein: 2/
```
It's kinda Dull -->AlfWeg's Userpage

JoeyC
Member
Posts: 252
Joined: November 7th, 2017, 1:43 pm
Division: C
State: TX

### Re: Machines B/C

Fg=Fs
mgsin(theta)=umgcos(theta)
sin(theta)=ucos(theta)
u=sin(theta)/cos(theta)
u = tan(theta)
u = ~.364
Ohayo!
`Dynamic Planet, Protein Modeling, Fast Facts, Thermodynamics`
`Dynamic Planet, Compound Machines, Chem Lab, WaQua (maybe), Ornith (maybe)`
1 Corinthians 13:4-7
Scientia Potentia Est

AlfWeg
Member
Posts: 89
Joined: July 22nd, 2019, 7:52 am
Division: C
State: MI

### Re: Machines B/C

Fg=Fs
mgsin(theta)=umgcos(theta)
sin(theta)=ucos(theta)
u=sin(theta)/cos(theta)
u = tan(theta)
u = ~.364
Last&SeventhYearOlympian
```NorView/CenterVille/UMICH/r/s:
Machines: 2/
DP: 1/
Code:X/
GeoMap:X/
Protein: 2/
```
It's kinda Dull -->AlfWeg's Userpage