Physics help

[terrytek]

So, I honestly hate this new lesson our physics teacher gave us. Freaking law of universal gravitation, which is like 6.67x10^-11 times the product of two masses divided by the distance squared. I honestly hate this freaking formula because it's so difficult to understand. I'll give you a problem.

 

Calculate the force between two touching grapefruits each with a radius of 0.08 metres and a mass of 0.45 kilograms.

 

I tried using the formula for law of universal gravitation but I keep getting the wrong answer. I was so pissed in class, i nearly cried. Was there something I did wrong? So after I squared the distance and multiplied the two masses together,  I divided the mass by the distance, then I multiplied that by the second part, the 6.67x10^-11. But the teacher is getting a different answer as me.

[Jerakl]

We're on that right now. It's easy IMO. I get most of it.

 

I'll see if I can find something like that in my phys book.

[Laederem]

Show your work?

 

are you using (2*(.08))^2 as your radius?

this is free points lad, you be happy you're working with formulas. 

[terrytek]

We're on that right now. It's easy IMO. I get most of it.

If it's easy, how come I'm not getting it? I'm genuinely sick of it.

[LukaP]

So, I honestly hate this new lesson our physics teacher gave us. Freaking law of universal gravitation, which is like 6.67x10^-11 times the product of two masses divided by the distance squared. I honestly hate this freaking formula because it's so difficult to understand. I'll give you a problem.

 

Calculate the force between two touching grapefruits each with a radius of 0.08 metres and a mass of 0.45 kilograms.

 

I tried using the formula for law of universal gravitation but I keep getting the wrong answer. I was so pissed in class, i nearly cried. Was there something I did wrong? So after I squared the distance and multiplied the two masses together,  I divided the mass by the distance, then I multiplied that by the second part, the 6.67x10^-11. But the teacher is getting a different answer as me.

you have to take double the radius, because you have 2 fruits

[mansoor_]

5.276*10^-10 N

[terrytek]

Show your work?

 

are you using (2*(.08))^2 as your radius?

Yes. Then, I multiplied the masses together and got 0.2025 KG as an answer. I divided that by 0.16^2 and got 7.91.

[Thunderjolt]

you have to take double the radius, because you have 2 fruits

 

Yep, What Luka said. From what I think "r" means it's the radius between the two objects. Since they're touching you should have the radius of both the objects together giving r= 0.16m

[terrytek]

Yep, What Luka said. From what I think "r" means it's the radius between the two objects. Since they're touching you should have the radius of both the objects together giving r= 0.16m

Yeah, I then squared 0.16 since you have to and got 0.0256 m.

[LukaP]

heres your answer

52.78E -11

[Flight1sim]

now, is terry really 16...

[LukaP]

now, is terry really 16...

hes 13...

[Flight1sim]

hes 13...

how are you people so sure?

[Laederem]

Yes. Then, I multiplied the masses together and got 0.2025 KG as an answer. I divided that by 0.16^2 and got 7.91.

You're entering your calculations wrong. If you're using a TI be sure you put brackets at the end of your xEn notation numbers, that could be affecting your answers if you're doing  something like 5E-11/r^2

 

I got the same answer of 5.27E-11  5.27E-10

 

If that's still wrong then ignore it because your teacher must have made a mistake, this isn't very complicated and there's nothing fancy you can do here. 

[terrytek]

heres your answer

52.78E -11

But my teacher wants to see the work. Right now, I'm stuck on Fg=(6.67x10^-11)(7.91)

 

hes 13...

No I ain't. Where did you get that assumption?

[LukaP]

G* (2m)/4(r^2) = G * m/2(r^2) = 52.78E -11

[terrytek]

You're entering your calculations wrong. If you're using a TI be sure you put brackets at the end of your xEn notation numbers, that could be affecting your answers if you're doing  something like 5E-11/r^2

 

I got the same answer of 5.27E-11

I have a Casio calculator, the FX series.

[LukaP]

But my teacher wants to see the work. Right now, I'm stuck on Fg=(6.67x10^-11)(7.91)

 

No I ain't. Where did you get that assumption?

umm, for some reason, thats what everyone thinks here

[LukaP]

But my teacher wants to see the work. Right now, I'm stuck on Fg=(6.67x10^-11)(7.91)

 

No I ain't. Where did you get that assumption?

thats not 7.91 its 35.something

[Thorium19]

Yep, did that in October, it's not too tricky is gravitation.

[Aniallation]

1 + 1 = a good phone

[terrytek]

thats not 7.91 its 35.something

Yeah right. My calculator, when I divided 0.2025 by 0.0256, got 7.91 something.

[LukaP]

Yeah right. My calculator, when I divided 0.2025 by 0.0256, got 7.91 something.

wait i did it wrong, its 7.91. are you using your G correclty?

[Laederem]

Yeah right. My calculator, when I divided 0.2025 by 0.0256, got 7.91 something.

dude no, it's (FMM)/r^2 not F(MM/r^2)

 

you're getting the wrong answer because you're doing g(.45^2/.16^2) instead of (g*.45^2)/.16^2

 

thats two exactly the same expressions

lol, whoops you're right

still have no idea what you're doing wrong

[LukaP]

dude no, it's (FMM)/r^2 not F(MM/r^2)

thats two exactly the same expressions