M1 June 2014 AQA Question 4 Part a)

In the mark scheme it says the distance travelled for part a is 20 meters whereas i think it should be sqrt 409. Could someone please explain to me why it is 20 meters?
Any help is much appreciated!

(edited 7 years ago)

Reply 1

Kieranf2107

The reason why its 20 is its the distance from origin to A.
For part a you ignore V because V only changes where you end up not the time taken

Reply 2

DubDub2011

The vertical distance to travel is 20m (Stated in the question as the width of the river) and you only have one vertical force which is 2sin(70) (This is found by equating the forces), hence as there is only one vertical force pushing the boat across the river and
Speed = Distance over Time
2sin(70) = 20t
Hence t = (2sin(70))/20

You're right in what you're saying that the distance traveled isn't 20m in total, but in terms of the vertical components, the boat only travels 20m

Also, good luck tomorrow, I'm sitting the same exam. :smile: