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Weather Rocket Problem

  • Thread starter bcjochim07
  • Start date
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1. Homework Statement
A small rocket to gather weather data is launched straight up. Several seconds into the flight, its velocity is 120 m/s and it is accelerating at 18 m/s^2. At this instant, the rocket's mass is 48 kg and it is losing mass at the rate of .5 kg/s as it burns fuel. What is the net force on the rocket? Hint: Newton's second law was presented in a new form in this chapter


2. Homework Equations
p=mv F=dmv/dt F=dp/dt


3. The Attempt at a Solution

I tried to come up with a formula for momentum with respect to time and then differentiate it to find force, but it's not making sense to me.

I tried to say that at this instant dm/dt= -.5 and dv/dt = 18 and then I tried to multiply those but that clearly is not correct reasoning. I'm pretty sure I'm not looking at this problem right. Any hints?
 
Last edited:

Answers and Replies

tiny-tim
Science Advisor
Homework Helper
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Welcome to PF!

I tried to say that at this instant dm/dt= -.5 and dv/dt = 18 and then I tried to multiply those but that clearly is not correct reasoning. I'm pretty sure I'm not looking at this problem right. Any hints?
Hi bcjochim07 ! Welcome to PF! :smile:

A hint? :rolleyes: … yes! …

Product rule: d(mv)/dt = mdv/dt + vdm/dt. :smile:
 
374
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Oh yes, I see. Thank you very much!
 

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