You walk 3 km east and then 4 km north. How far are you from the start? The answer is 5 km, and not 7 km. In this course we learn why. We separate scalars from vectors, we add and subtract vectors with arrows and with numbers, and we split any vector into two parts along the axes, which makes hard problems easy.
3 lessons, about 1 h 30 min3 simulations12 problems6 practice questionsPython in every lesson
A scalar has a size only. A vector has a size and a direction, and adds by the triangle rule. Multiplying a vector by a number changes its length, and a negative number also turns it round. A unit vector only shows a direction. Displacement is a vector, but distance is a scalar.
Vectors add head to tail (the triangle law), or as the diagonal of a parallelogram. The size of the sum is , where is the angle between the vectors, so it lies between and . To subtract a vector, add its opposite.
We split a vector into an part and a part: and . With the unit vectors and , . To add vectors, add the parts and the parts separately. The signs of the parts tell you which quarter the vector points into.
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