Force Acceleration Weight

  • Thread starter Peach
  • Start date
  • #1
Peach
80
0

Homework Statement


A spacecraft descends vertically near the surface of Planet X. An upward thrust of 25.0kN from its engines slows it down at a rate of 1.20m/s^2, but if an upward thrust of only 10.0kN is applied, it speeds it up at a rate of .80m/s^2. Apply Newton's second law to each case, speeding up or slowing down, and use this to find the spacecraft 's weight near the surface of Planet X.


Homework Equations


F = ma


The Attempt at a Solution


Okay, I'm confused about how if 25.0kN force is applied, then it slows down but 10.0kN part will speed it up. I guess maybe that's why my method is wrong and I keep getting the wrong answer. This is what I'm doing: since I have the force and acceleration, I converted kN to N and divided by its acceleration to find the mass. Then I take the mass x gravity = weight, converting it back kN. Pls help me, where did I go wrong?
 

Answers and Replies

  • #2
denverdoc
963
0
Another poorly worded problem if that's quoted accurately. Is the right answers 2.13(7500)=15975?
 
Last edited:
  • #3
Peach
80
0
Yeah, I copied it word for word. I don't have the right answer but um, how did you get those numbers?
 
  • #4
denverdoc
963
0
well what the question supposes(and its poorly worded) is "it" is the planets gravitational pull. In one case it retards the spacecraft s upwards acceleration so that the net acceleration is up, and in the second case the gravitational pull overcomes the thrust of the rocket. In each case, try to develop an eqn for the given net a in terms of the rocket thrust and unknown g constant of the planet. Should have 2 eqns, 2 unknowns.
 
  • #5
Peach
80
0
Ah, if you didn't explain, I don't think I'd understand the problem...I got it now, thank you very much.
 
  • #6
denverdoc
963
0
My pleasure, I just can't resist a rocket problem!
John
 

Suggested for: Force Acceleration Weight

Replies
13
Views
204
  • Last Post
Replies
3
Views
451
Replies
59
Views
1K
  • Last Post
Replies
21
Views
229
Replies
5
Views
263
Replies
4
Views
472
Replies
6
Views
1K
Replies
6
Views
896
Replies
22
Views
1K
Top