(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Comet moves around the sun in a very ellipical orbit around the sun. As it approach, in 1986, Comet Halley was 8.79x10^7km from the sun and moving with a speed of 54.6km/s. What will be the comet's speed be when it crosses Neptune's orbit in 2006?

length of comet from the sun = 8.79x10^7km = 8.79x10^10 m

v of comet = 54.6km/s = 54.6x10^3m/s

T = 20 years

length of neptune from the sun = 4.50x10^12m

2. Relevant equations

i use the equation T^2 = (4*pie*r^3)/GM and K2 + U2 = K1 + U1

3. The attempt at a solution

i first use the Kelper's rule to find M of the comet, but i don't really know if that's the right step to start with.

Thank you.

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# How to calculate the comet's speed?

**Physics Forums | Science Articles, Homework Help, Discussion**