Posted by Dreskillz89 on Sunday, September 20, 2009 at 3:59pm.
A small 7.10kg rocket burns fuel that exerts a time-varying upward force on the rocket. This force obeys the equation F = A + Bt^2. Measurements show that at t = 0, the force is 121.0N, and at the end of the first 2.10s , it is 176.0N.
Find the net force on this rocket the instant after the fuel ignites.
Find the acceleration of this rocket the instant after the fuel ignites.
Find the net force on this rocket 4.10s after fuel ignition.
Find the acceleration of this rocket 4.10s after fuel ignition.
I found out that
A = 121.0 N
B = 12.5 N/s^2
Net Force = 51.42 N
Acceleration = 7.24 m/s^2
Part C and Part D is what I am having trouble with.
- Physics - Dreskillz89, Sunday, September 20, 2009 at 4:05pm
By the way, the A = 121.0 and B = 12.5 refers to the equation F=A+Bt^2, not Part A and Part B.
- Physics - MathMate, Sunday, September 20, 2009 at 4:32pm
A, B, are correct.
a) and b) are also correct.
For part (c), the question is asking for the force, F(t) = A+Bt², using the values of A and B that you have found earlier, and t=4.1 s. F(4.1) should be over 300 m/s/s.
Once you have calculated the force, you can proceed to calculate the acceleration as in part b).
- Physics - Dreskillz89, Sunday, September 20, 2009 at 8:36pm
For Part C, I calculated it to be 331.125N, but am still getting a wrong answer. I know you said it was over 300, is that what you got too?
- Physics - MathMate, Sunday, September 20, 2009 at 9:40pm
I have the same number as you have, but based on your values of A and B, which I found minor discrepancies. If it is a computer answer, you may want to recheck from there on.
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