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VCE Stuff => VCE Science => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Physics => Topic started by: methodsboy on February 27, 2009, 06:26:56 pm

Title: Gravity and Satellites
Post by: methodsboy on February 27, 2009, 06:26:56 pm: Hey
im in a bit of a pickle with this one:
Neptune has a mass of: 1.02 x 10^26 kg
It's moon, Triton has mass : 2.14 x 10^22 kg and has an orbital radius of 3.55 x 10^8 m
For triton, calculate its:
- orbital acceleration

The answer is 5.40 x 10^-2 m/s^2 but i keep getting it wrong.

Anyone out here willing to help?
Title: Re: Gravity and Satellites
Post by: methodsboy on February 27, 2009, 06:39:40 pm: Mao? True Tears? Edmond? ANYONE???????
Title: Re: Gravity and Satellites
Post by: Mao on February 27, 2009, 06:46:22 pm: orbital acceleration as in centripetal acceleration, i.e. Neptune's gravitational field strength at the orbital radius

$g = \frac{GM}{R^2} = \frac{(6.67E-11)\times (1.02E26)}{(3.55E8)^2} = 0.0540\; ms^{-1}$
Title: Re: Gravity and Satellites
Post by: Edmund on February 27, 2009, 06:47:33 pm: I think:

Use F = G.Mm / r^2

Then, F = ma, where m is mass of Triton

EDIT: Yeah look at Mao's... I don't know how to use Latex...
Title: Re: Gravity and Satellites
Post by: methodsboy on February 27, 2009, 07:58:09 pm: Quote from: Mao on February 27, 2009, 06:46:22 pm
orbital acceleration as in centripetal acceleration, i.e. Neptune's gravitational field strength at the orbital radius

$g = \frac{GM}{R^2} = \frac{(6.67E-11)\times (1.02E26)}{(3.55E8)^2} = 0.0540\; ms^{-1}$
where did u get 6.67E -11 from?
Title: Re: Gravity and Satellites
Post by: TrueTears on February 27, 2009, 08:13:24 pm: Quote from: methodsboy on February 27, 2009, 07:58:09 pm
Quote from: Mao on February 27, 2009, 06:46:22 pm
orbital acceleration as in centripetal acceleration, i.e. Neptune's gravitational field strength at the orbital radius

$g = \frac{GM}{R^2} = \frac{(6.67E-11)\times (1.02E26)}{(3.55E8)^2} = 0.0540\; ms^{-1}$
where did u get 6.67E -11 from?
Remeber G is a constant, better known as universal gravitational constant, $G = 6.67 \times 10^{-11}$
(obviously this is different from g, small case, which is 9.8 $ms^{-2}$ )
Title: Re: Gravity and Satellites
Post by: methodsboy on February 27, 2009, 08:15:02 pm: oh LOL sorry.... i was meant to say 1.02 x 10^26.
just realized that M is for the bigger mass hence 1.02 x 10^26
b4 i kept using mass of triton and thats why i didnt get anywhere
Thanks all :)
Title: Re: Gravity and Satellites
Post by: TrueTears on February 27, 2009, 08:16:36 pm: Quote from: methodsboy on February 27, 2009, 08:15:02 pm
oh LOL sorry.... i was meant to say 1.02 x 10^26.
just realized that M is for the bigger mass hence 1.02 x 10^26
yah, remember the M (capital M) is always the mass of the object being orbited. So like for the moon orbiting around the earth, M would be the mass of the earth. Or for earth orbiting around the sun, M would be the mass of the sun.