ACTIVITY 2.8
VECTORS AND FORCES. AN EXAMPLE: A BOAT IN A CANAL

Another application of the vectors is to represent physical magnitudes that they have module and direction, and that they add applying the parallelogram law, as speeds, accelerations and forces. In this unit, we will centre on the forces and we suppose that you are something familiarized with them and with his units.

Sum of two or plus forces it is called resulting. In the next unit we will see what we must make to calculate the module of a vector sum. Nevertheless, there are two cases in which to obtain the module from the resulting of a sum is very easy:

1) When the forces have the same direction. Then:
- If the forces have the same way, the module of the sum is the module sum
- If the forces have opposite way, the module of the sum is the module difference

2) When forces are perpendicular we can apply Pythagoras's theorem. If, as usual, we indicate the vector module with the notation||, and and They are perpendicular, we can write:
                                                         |+|² =||² +||²

INTERACTIVE ACTIVITY

A boat must move by a canal with the help of two forcesand of 3 kN and 4 kN respectively (kN are 1000 Newton). We want to get the components of these forces in order that the boat will move in straight along the canal. You try to get it of the three following forms:

1) Without varying the forceand modifying the direction of the force. That is to say, moving the end only of the force.

2) You update this web page and repeats the exercise, now without varying the forceand modifying the direction of the force.

3) You update this web page again and repeats the exercise varying the two forces simultaneouslyand.
                            SOLUTION

END OF ACTIVITY 2.8
VECTORS AND FORCES. AN EXAMPLE: A BOAT IN A CANAL