ATAR Notes: Forum

VCE Stuff => VCE Science => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Physics => Topic started by: coletrain on March 05, 2010, 04:16:33 pm

Title: coletrains' physics questions
Post by: coletrain on March 05, 2010, 04:16:33 pm: A rocket is disabled at a height of 9 radii above the surface of the Earth. It is moving very slowly. By how much will its velocity change in the next 200s? (Take g at the surface of Earth as 10m/s/s, and assume that the local value of g does not change in the 200s)
Title: Re: coletrains' physics questions
Post by: /0 on March 05, 2010, 04:30:39 pm: $a = \frac{GM}{R^2}$ , so $aR^2 = constant$ (or $a_1R_1^2 = a_2R_2^2$ )

Therefore, if we take an earth radius to be $R_E$ , then

$(10)(R_E)^2 = (a_2)(10R_E)^2$

$10 = a_2(100)$

$a_2 = 0.1\ \mbox{ms}^{-2}$

Then apply $\Delta v = a_2\Delta t$
Title: Re: coletrains' physics questions
Post by: coletrain on March 05, 2010, 04:37:22 pm: thanks, here's another one

A small satellite orbits Mars. It has a kinetic energy of 3.0 x10^10 J, and is at constant distance of 8.0 x 10^7m from the center of Mars. What is the weight of the satellite at this height.
Title: Re: coletrains' physics questions
Post by: appianway on March 05, 2010, 04:44:19 pm: I think this is how you do it.

K = mv^2/2
Weight force = centripetal force = mv^2/r
Thus 2K/r = weight force