You are Here: Home >< Maths

Mechanics watch

1. I just can't seem to draw resultant velocity triangles correctly.
I have just done a question from January 2006 and the mark scheme uses the diagram
(The question asks to find V).
I however drew it differently so I still had an included angle but on my diagram that angle was 45.
I just don't seem to be able to understand how you know where to draw the different velocities.
Many thanks
2. (Original post by orange8120)
I just can't seem to draw resultant velocity triangles correctly.
Could you provide the question?
3. (Original post by Zacken)
Could you provide the question?
4. (Original post by orange8120)
For 1 (a) (i), try to use trigonometry for right angled triangles. For part 1 (a) (ii), try now to use the fact that this a right angled triangle to work out v.

For (b), a force diagram is certainly useful. You say in the OP you struggle with this. The way I would approach this would be to literally squash the forces together.

So place the line for the velocity of the water going into the line representing the velocity of the boat. Then my resultant will be the line connecting these two vectors, so to make a resultant force triangle (see my diagram).

This triangle is not right angled and so you need to consider how you work out the lengths of the sides of a right angled triangle. The angle between the two sides can be worked out using basic geometry.

Let me know if you need any further help!
Attached Images

Related university courses

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: March 18, 2016
Today on TSR

Edexcel C4 Maths Unofficial Markscheme

Find out how you've done here

917

students online now

Exam discussions

Poll
Useful resources

Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

How to use LaTex

Writing equations the easy way

Study habits of A* students

Top tips from students who have already aced their exams

Chat with other maths applicants