I.5.3.2. Parallelogram rule
📚
Parallelogram rule is used for the addition of two nonlinear vectors which have the same point of application, by going through the following four steps:
- Draw the two vectors so that they have the same point of application.
- With the segments of the 2 vectors, a parallelogram is formed (quadrilateral with parallel and equal opposite sides).
- Draw the diagonal of the parallelogram that has a common point with the two vectors. This segment represents the resulting vector, which is noted and an arrow is placed at the end.
- With the ruler we measure the segment of the resulting vector and with the simple rule of three, we find its numerical value.
🔓 Solved problem
1. A river flows east at a speed of 60 km/h. A boat goes on the river in its direction of flow at a speed of 100 km/h, in a direction that makes an angle of 30° to the river bank. What is the speed of the boat towards the shore? Graphs using the following scale: 1 cm: 20 km/h.
Solution:
v1 = 60 km/h, horizontal direction, to the right
v2 = 100 km/h, direction that makes an angle of 30° with the horizontal, upwards.
Standard: 1cm : 20 km/h.
