- To add (i.e. find the resultant of) two or more force vectors acting at the same point:
- arrange the force vectors in ‘nose-to-tail’ formation
- find the magnitude and direction of the vector from the beginning of the first vector to the end of the last.
- speed is a scalar quantity, whilst velocity is a vector quantity.
- a velocity vector can be represented by an arrow.
- direction represents direction of travel (obviously)
- length represents magnitude (speed of travel)
- example question
- you can paddle a canoe at 5km/h in still water and you want to cross a river which is 50 m wide. The river is flowing at 3km/h
- if you start from A and paddle directly towards the opposite bank, find the resultant velocity, the time taken to reach the bank and how far you are from B when you arrive.
- add velocity vector of the river, to the velocity vector of the canoe.
- 5.83km/h, 36 seconds, 30 metres.
- you can use trig to solve it, but it is easier under the knowledge that the ratio of sides is the same between the two triangles. (e.g. two angles in common, by the AA test, they are similar triangles)
- god im so tired
- what if example question, but you have to land on point b
- 58.309… m need to travel (at 5km/h) so 45 seconds travel
- use trig (sohcahtoa) to find angle (direction of travel)
Ex 3C ODD Qs