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

Work and vectors

1. Homework Statement

A force F = (2.7i + 3.2j) N is acting on a particle while it travels from the point (x, y) =
(1, -1) m to the point (2, 1) m. Find the work done by the force F on the particle.

2. Homework Equations
W=FD and A=SqRt of Ax^2+Ay^2

3. The Attempt at a Solution
ok i used the right triangle to find the resultant vector of the force F by squaring both the 2.7 and 3.2 then adding them and take the square root i got 4.18 so that should be the F in W=FD and then i foudn teh reultant vector of the coordinates 1,-1 and 2,1 and got square root of 5. which should be the distance and then i multiplied 4.18 and radical 5 and got 9.34 which is wrong.. where did i go wrong? btw 9.10 is the answer
 

alphysicist

Homework Helper
2,238
1
Hi silentsaber,

1. Homework Statement

A force F = (2.7i + 3.2j) N is acting on a particle while it travels from the point (x, y) =
(1, -1) m to the point (2, 1) m. Find the work done by the force F on the particle.

2. Homework Equations
W=FD and A=SqRt of Ax^2+Ay^2

3. The Attempt at a Solution
ok i used the right triangle to find the resultant vector of the force F by squaring both the 2.7 and 3.2 then adding them and take the square root i got 4.18 so that should be the F in W=FD and then i foudn teh reultant vector of the coordinates 1,-1 and 2,1 and got square root of 5. which should be the distance and then i multiplied 4.18 and radical 5 and got 9.34 which is wrong.. where did i go wrong? btw 9.10 is the answer
The problem is that the formula for work is not [itex]W=Fd[/itex] (product of magnitudes of force and displacement), it is

[tex]W=\vec F\cdot\vec d[/tex]

(dot product of force and displacement vectors). Are you familiar with the dot product? If so, then once you find the two vectors involved the problem is quite straightforward.
 
141
1
You're working with vectors. So you need to find the dot product. W = F dot D.
 
thankyou guys very much i totally forgot the dot product existed XD
 

Related Threads for: Work and vectors

  • Posted
Replies
3
Views
566
  • Posted
Replies
1
Views
718
  • Posted
Replies
11
Views
2K
Replies
7
Views
3K
C
Replies
4
Views
1K

Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving
Top