Hi

i need help on the following questions:

1)if a=4i + 3j - k, b= 2i - 4j +3k, c = 2i +k find 1.5c - b +0.5a:

$\displaystyle =1.5(2i+k)-2i-4j+3k+0.5(4i+3j-k)$

$\displaystyle =3i+1.5k-2i-4j+3k+2i+1.5j-0.5k$

$\displaystyle =3i-2.5j-2k$

Now the answer says its 3i+(11/2)j-2k, however i don't understand how they got this.

2)In moving a crate of electrical fittings, a force F of magnitude 84 newton is applied in the direction of b, where b=3i-2j+6k

If the create is moved point A(-2, -1, 1) to the point B(1,1,2) measured in meters, find the work done.

$\displaystyle W= F . \vec{AB}$

$\displaystyle \vec{AB} = \vec{OB} - \vec{OA}$

$\displaystyle =i+j+2k--2i-j+k$

$\displaystyle =3i+2j+k$

i problem i have is what is the force? is it 84 or is it b=3i-2j+6k?

3) The angle between x and y is arcos (4/21). Find the scalar t given that:

$\displaystyle x=6i+3j-2k$ and $\displaystyle y=-2i+tj-4k$

Lastly just a side question from vectors, how would covert 1.11m/s into minutes and seconds?

P.S