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Net Force of object changing velocity

  • Thread starter ital_dj
  • Start date
31
0
[SOLVED] Net Force of object changing velocity

Hi, I'm studying for a test, so there might be a few of these in the next hour or so.

1. Homework Statement
A supertanker of mass 1.0 X 10[tex]^{8}[/tex] kg travels 3.5km, reaching a speed of 4.1km/h from rest. What was the magnitude of the unbalanced force acting on it?

2. Homework Equations
Fnet = ma
v[tex]^{2}_{2}[/tex] = v[tex]^{2}_{1}[/tex] + 2a[tex]\Delta[/tex]d


3. The Attempt at a Solution
I tried (4.1km/h)[tex]^2[/tex] = 2a(3.5km)
[tex]\frac{16.81km/h^2}{3.5km}[/tex] = 2a
4.80km = 2a
2.4km/h = a

and then I tried converting it by dividing it by 60 twice, and sliding to the right 3 decimal places, then inserting it into the Fnet = ma.

I'm really stuck, and that's not good if I have a unit test tomorrow :frown:
 
Last edited:

Answers and Replies

rock.freak667
Homework Helper
6,230
31
When using F=ma, you need m to be in kg and a to be in m/s^2
So, convert the velocities into m/s and the distance into m
 
31
0
I'll try it again but instead beforehand.. I did it after, though, does that make a difference?
EDIT: still not working out though.
 
Last edited:
rock.freak667
Homework Helper
6,230
31
I'll try it again but instead beforehand.. I did it after, though, does that make a difference?
Not really but it seems correct that [itex]a=2.4kmh^{-2}[/itex]. Just multiply by 1000 and divide by 3600 and it should be correct.
 
Last edited:
31
0
The answer in the book is 1.9 * 10[tex]^4[/tex]

By multiplying 2.4 times 1000 and dividing by 3600 gives me 0.67. Still not correct. :S
 
rock.freak667
Homework Helper
6,230
31
The answer in the book is 1.9 * 10[tex]^4[/tex]

By multiplying 2.4 times 1000 and dividing by 3600 gives me 0.67. Still not correct. :S
Divide by 3600^2 . Sorry,told you to do the wrong thing.
 
31
0
OK Thanks.
 

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