c4l3b said:Another question from A-level Maths book;
Find the work done by a force F = 2i + k in moving an object from the point A with coordinates (3, 4, 0) to the point B with coordinates (2, 5, -1)
How do i implement F x S? <<< You don't!! The equation for work done is W = F • S
I am assuming you apply the parallelogram law? - No - law of parallelogram is used for addition of vectors
Vector F is already defined for you.
Define vector S - from the co-ordinate points given
Then perform dot product.
.
c4l3b said:Define vector S........... AB = OB - OA?
s = AB = OB - OA
= (2, 5, -1) - (3, 4, 0)
= - i + j - k
Therefore work done force F = 2i + k is
Work done F • S = (2i + 0j + 1k)•[(-1) i + 1j + (-1)k] =| [2*(-1)] + [0*1] + [1*(-1)] |= |-2 -1| = 3
Please review Vector Product
Subhotosh Khan said:c4l3b said:Define vector S........... AB = OB - OA?
s = AB = OB - OA
= (2, 5, -1) - (3, 4, 0)
= - i + j - k
Therefore work done force F = 2i + k is
Work done F • S = (2i + 0j + 1k)•[(-1) i + 1j + (-1)k] =| [2*(-1)] + [0*1] + [1*(-1)] |= |-2 -1| = 3 -- isn`t that -3 [units] :?:
Please review Vector Product