IGCSE/GCSE/O & A Level/IB/University Student Forum

Qualification => Subject Doubts => GCE AS & A2 Level => Sciences => Topic started by: helllife on January 29, 2010, 03:30:48 pm

Title: gravitation doubt...
Post by: helllife on January 29, 2010, 03:30:48 pm

1)An object projected at 127m/s upward from a small moon reaches a height of 5.03 km. If the radius of the moon is 1820km, calculate its mass.

i just dnt knw how to work it out...can  anyone please tell me the answer and shows the working? i would appreciated if anyone do so.

Title: Re: gravitation doubt...
Post by: astarmathsandphysics on January 29, 2010, 03:41:21 pm

I will do it when I get home

Title: Re: gravitation doubt...
Post by: astarmathsandphysics on January 30, 2010, 12:43:39 pm

1)An object projected at 127m/s upward from a small moon reaches a height of 5.03 km. If the radius of the moon is 1820km, calculate its mass.
KE=increase in GPE
1/2mv^2=GMm(1/r1-1/r2)
m cancels to gicve 1/2v^2=GM(1/r1-1/r2)
1/2*127^2=6.67*10^-11*M*(1/(1820000)-1/(182000+5030))=M*1.01*10^-19
M=8064.5/1.01*10^-19 =7.98*10^22 kg

Title: Re: gravitation doubt...
Post by: helllife on January 30, 2010, 04:28:42 pm

thank you!!!

i may ask some more question later on..... :)

Title: Re: gravitation doubt...
Post by: astarmathsandphysics on January 30, 2010, 05:00:38 pm

If I can make a topic out of it I might make a page on my website