rocket problem: time to travel from point A to point B

[walt111]

t (time) is similar to m(mass) x Ve (exhaust velocity) x delta V divided by 2P(power)

power is 1000 watts, mass is 100kg, delta v is 5 km/s, Ve is 16 km/s

I don't understand how they get the answer of 1.5 months

Thanks,

Walt

 

[jonboy]

What is are we trying to solve for? Please write the direct question and show all work you have done.

Also is the equation: (1)\(\displaystyle \L t = (m)(Ve)\frac{{(\Delta v)}}{{2^p }}\) or (2)\(\displaystyle \L t = \frac{{(m)(Ve)(\Delta x)}}{{2^p }}\)

?? Please reclarify

Thankees

 

[mcrae]

...wont both equations give the same answer?....

if he doesnt understnad how to get the answer of 1.5 months, i believe we are trying to solve for time

 

[jonboy]

No because in one you are only dividing Delta V by 2^p and the other is divinding everything on the left of the equals by 2^p. I guess you would be solving for time then.

 

[mcrae]

its not 2^P, it is 2P
power is measured in watts which is 1000 kg·m^2·s^(−3)
mass is 100 kg
v is 5 km/s which is 5000 m/s (convert to m/s because watts uses meteres, not km)
Ve is 16 km/s which is 16000 m/s(convert to m/s because watts uses meteres, not km)

usiing the equation T= (mass)(Ve)(delta v)/2P
T(in seconds)= (100)(16000)(5000)/2(1000)
=8000000000/2000
=4000000 seconds

4000000/3600 = 1111.1 hours

1111.1/24 = 46.29 days

46.29/30 = 1.543 =1.5 months