• Support PF! Buy your school textbooks, materials and every day products Here!

Forces, displacement, and coordinates of a particle

  • #1

Homework Statement



Two forces, vector F 1 = (4 i hat bold + 6 j hat bold) N and vector F 2 = (4 i hat bold + 8 j hat bold) N, act on a particle of mass 1.90 kg that is initially at rest at coordinates (+1.95 m, -3.95 m).

A) What are the components of the particle's velocity at t = 10.3 s?
Answer: 43.3i+75.9j
B) What are the components of the particle's velocity at t = 10.3 s?
Answer: 60.29°
C) What displacement does the particle undergo during the first 10.3 s?(Δr)

D) What are the coordinates of the particle at t = 10.3 s?

Homework Equations





The Attempt at a Solution


For C) I have tried every method I could think of to solve for Δr from multiplying the components of the particles velocity (A) by the time, to squaring each part and placing them under a √
D) I tried a lot for D too. I tried multiplying the coordinates given in the problem above by time, multiplying by the velocity components, and some other methods I cant remember, but nothing has come out right.
 

Answers and Replies

  • #2
6,054
390
The section titled "relevant equations" is there for a reason. What equations are relevant in this case?
 
  • #3
The section titled "relevant equations" is there for a reason. What equations are relevant in this case?
If i knew I would use them

For A) I used F=ma
Vf=Vi+at
For B) I used arctan (Vxf/Vyf)

For C) the equation I thought might be right was rf=ri + Vit + 1/2at^2, but that was wrong

And for D) I tried to multiply the time by the velocity components because the seconds would cancel out and I'd be left with meters
 
  • #4
6,054
390
The equation you mentioned for C) is indeed the equation you should have used. What was the problem with it?
 
  • #5
The equation you mentioned for C) is indeed the equation you should have used. What was the problem with it?
Im not sure, I can try it again
I think I may have been confused on what numbers get plugged in where

So t=10.3s
a=4.21i+7.36j m/s^2
Vi=0?
And then im solving for rf-ri

Is that all correct?
 
  • #6
6,054
390
You will obtain the displacement vector. It is not entirely clear to me whether C) wants that, or its magnitude, though.
 
  • #7
Its asking for Δr in meters
 
  • #8
6,054
390
Then it is probably the magnitude.
 
  • #9
Then it is probably the magnitude.
Thats where you square the values and put them under the radical sign right?
 
  • #10
6,054
390
Right.
 
  • Like
Likes 1 person
  • #11
Ok sorry for all the questions but i just wanna make sure im gonna do this right

So I solve for Δr and put those under the radical sign?
But since those are vector components I cant add them together
Am i putting the wrong values under the rad sign?
 
  • #12
6,054
390
If you are given a vector ## a \vec \imath + b \vec \jmath##, what is its magnitude?
 

Related Threads on Forces, displacement, and coordinates of a particle

Replies
14
Views
4K
  • Last Post
Replies
9
Views
659
  • Last Post
Replies
5
Views
4K
  • Last Post
Replies
12
Views
2K
  • Last Post
Replies
1
Views
1K
  • Last Post
Replies
0
Views
1K
  • Last Post
Replies
2
Views
1K
  • Last Post
Replies
2
Views
2K
Replies
16
Views
1K
Top