Work problem with vector notation! Help please

  • Thread starter od943
  • Start date
1. The problem statement, all variables and given/known data
PART A: A force ~F = Fx ˆı+Fy ˆ acts on a particle that
undergoes a displacement of ~s = sx ˆı + sy ˆ
where Fx = 6 N, Fy = −3 N, sx = 5 m, and
sy = 1 m.
Find the work done by the force on the
particle.
Answer in units of J.

PART B: Find the angle between ~F and ~s.
Answer in units of ◦.

PART C: An easy question but still need help:
Which of the following does not involve work?
1. A golf ball is struck.
2. A weight lifter does military presses (lift-
ing weights over his head.)
3. A professor picks up a piece of chalk from
the floor.
4. A runner stretches by pushing against a
wall.
5. A child is pushed on a swing.

2. Relevant equations
a^2+b^2=c^2
F=ma
W=fcosthetad

3. The attempt at a solution
1. The problem statement, all variables and given/known data



2. Relevant equations



3. The attempt at a solution
 
so here's my try: i made two triangles...one out of the force vectors and another out of the displacement vectors
i found the resultant displacement vector to be 5^2+1^2=26...so 5.1 m
i found the resultant force vector by doing 3^2+6^2=45...so 6.7 N

if i plug in these numbers into the work equation of W=fdcostheta i'll get W=5.1m*6.7Ncostheta
to find theta i'll do the tantheta=1m/5m or 11.3099 degrees or 348.69 degrees when put in the correct coordinate plane....
so does W=5.1m*6.7Ncos348.69? that equals 33.5 joules.
 

Want to reply to this thread?

"Work problem with vector notation! Help please" You must log in or register to reply here.

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 Threads

Top