Work

Jul 2008
179
1
One particle moves in a straight line suffering a displacement d = (8m) + i cj while being subjected to a force F = (2N) i-(4N) j. (Other forces also act as particle). What is the value to c so that the work done by F on the particle is (a) zero (b) positive (c) negative



Answer:
(a) c=4m
(b) c<4m
(c) c>4m
 

werehk

PHF Hall of Fame
Apr 2008
886
180
HK
One particle moves in a straight line suffering a displacement d = (8m)i + cj while being subjected to a force F = (2N) i-(4N) j. (Other forces also act as particle). What is the value to c so that the work done by F on the particle is (a) zero (b) positive (c) negative



Answer:
(a) c=4m
(b) c<4m
(c) c>4m
For first case, work done equals zero which means that
\(\displaystyle F(d) = 0
\)
\(\displaystyle (8i+cj )(2i -4j) = 0
\)
\(\displaystyle 16 -(4c)j = 0
\)
\(\displaystyle c=4
\)

For other cases, chaning only the equal sign to inequality sign, you could get the answer without difficulties
 
  • Like
Reactions: Apprentice123
Jul 2008
179
1
For first case, work done equals zero which means that
\(\displaystyle F(d) = 0
\)
\(\displaystyle (8i+cj )(2i -4j) = 0
\)
\(\displaystyle 16 -(4c)j = 0
\)
\(\displaystyle c=4
\)

For other cases, chaning only the equal sign to inequality sign, you could get the answer without difficulties

Thank you for help
 

werehk

PHF Hall of Fame
Apr 2008
886
180
HK
welcome. (Smile)