# Work

#### Apprentice123

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

(a) c=4m
(b) c<4m
(c) c>4m

#### werehk

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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

(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

Apprentice123

#### Apprentice123

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

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