Asked by Hil

Hi, Greco. I am using the following formula to solve Ballistic Missile: sqrt(5*G*m_1/4*r_1). Given the following: m_1=5*10^24kg; r_1=6000;alpha=30 degrees;r_2=(5/2)r_1; G= 6.674*10^-11kg/m^3s^-2.
I thought I did it correctly using the proper formula.
My answer was incorrect. I have one shot left. I might not be using the formula correctly. Please help.
Answered by ROMA
Hi Hil, can you help me in rocket problem please? I used correct formula but I don't know how to find m_0/m? It is given 10% of mass in 290s and asking v in 145 s?
Answered by Hil
Hi, Roma. I am having the same problem as you. If I find out I will let you know. I am still trying to solve the problem on the missile.
Answered by ROMA
Hi hil, I did missile problem and I am seeing you are typing correct formula. Just remember to convert r_1 in meter( I think you did) and do calculate in your own calculater, not in edx one. Because sometimes I get wrong when I did in edx one calculator. may be we type sometimes in a wrong way.
Answered by Anonymous
hey guy, note that the radius is in km for the ballistic question.
for the propulsion question v_f=v_e*LN(m_1/m_f)
Answered by Andy
Hi, guys! What's about doppler shift? Can u tell me formulas?
Answered by ROMA
Hi Anonymous, I know the formula for propulsion, but I don't know how to find m_1/m_f in 145sec. It is given that 10% of mass in 290sec. can you tell how to find?
Answered by Anonymous
it ends up being 1/((1-(the percentage of mass loss)
Answered by ROMA
you mean 10/9? I already used this and got wrong. Can you do in the way how you did? I mean can you show here please?
Answered by Greco
Hil your answer should be 8337.92 m/s
Answered by Hil
Hi, Greco. Thanks I got the same answer on the second try.
Answered by ROMA
Hi Greco, can you do rocket problem pls?
Answered by Greco
yes ROMA
V= u*ln(1/(1-p))
a= V/t
Answered by kumar
Greco plz help ! i try using that formula but is not working
this is my question

Consider a rocket in space that ejects burned fuel at a speed of vex= 2.0 km/s with respect to the rocket. The rocket burns 11 % of its mass in 250 s (assume the burn rate is constant).

(a) What is the speed v of the rocket after a burn time of 125.0 s? (suppose that the rocket starts at rest; and enter your answer in m/s)

v=

incorrect
(b) What is the instantaneous acceleration a of the rocket at time 125.0 s after the start of the engines?(in m/s2)

a=
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