If a person pulls on a cart to the right with a force of 10 newtons and a second person pulls to the left with a force of 3 newtons what is the net force + direction on the cart

The plus direction is going to go with the 10N to the right. Since the second force is applied in exactly the opposite direction, the net force 10 - 3 = 7 newtons to the right.

as a general rule, scissors have blades less than 6 in (15 cm) long and usually have handles with finger holes of the same size. shears have blades scissors used to cut hair or fabric must be much sharper.

no. dot product   =0 when vecs at right angles