You take a 10 N block and lift it 1 meter vertically from the floor and then place it back down on the floor. How much work do you do during this motion?

Question

W = F x d x cos(theta)
So lifting it does work and the lowering it does negative work won't that cancel out to get OJ of work

Answer 1

Don't know how much work "I" do during this motion because I don't have the equations to calculations human work done during physical activities.
However, work done on the 10N block is zero, the way you calculated it.
When you lift the block, you are doing positive work because θ = 0°, so cos(θ)=1. When you lower the block back to the floor, force is still upwards (against gravity) and displacement is negative (cos(θ)=-1), so work is negative. All in all, there is zero work done (on the block).
The other way to look at it is that the displacement (xf-xi)=0, so work done
=F.D=0 (both are vectors, but scalar multiplication)