Need help with part of a physics q

lilolil_1

Hi guys - am new here but really in a bit of a situation. Studying for a maths exam and been given a previous paper and the following is part of one of the questions! I have the rest of the paper covered. Really could do with the help please! I'm 39 and back studying maths after 20 years out of school and two babies under 2 running around under my feet!!!!

here goes....

A bouy lies 1000metres east and 2000m north of a start line. A sailboat starts at start line and travels on a bearing of 045deg at 6ms-1. After 6 mins the boat turns immediatly and increases speed tp 9ms-1. How long does it take boat to reach the buoy?

There are no wind factors, no monsters in the sea to avoid and nothing else to slow the sailboat down!:P

Just someone to point me in the right direction would be enough!

Morbert

lilolil_1 wrote: »

Hi guys - am new here but really in a bit of a situation. Studying for a maths exam and been given a previous paper and the following is part of one of the questions! I have the rest of the paper covered. Really could do with the help please! I'm 39 and back studying maths after 20 years out of school and two babies under 2 running around under my feet!!!!

here goes....

A bouy lies 1000metres east and 2000m north of a start line. A sailboat starts at start line and travels on a bearing of 045deg at 6ms-1. After 6 mins the boat turns immediatly and increases speed tp 9ms-1. How long does it take boat to reach the buoy?

There are no wind factors, no monsters in the sea to avoid and nothing else to slow the sailboat down!:P

Just someone to point me in the right direction would be enough!

Where does the boat turn to after 6 mins? Towards the buoy?

lilolil_1

Morbert wrote: »

Where does the boat turn to after 6 mins? Towards the buoy?

Yes sorry! Should have said that! Thanks!

Morbert

The first step is to find out where the boat will be in 6 minutes.

Speed u = 6 m/s

It will travel north at a speed of 6 sin(45)
It will travel east at a speed of 6 cos(45)

lilolil_1

Have work out to be 5.82mins? Am i right?

Morbert

How did you arrive at 5.82? I can show you where you might have gone wrong with your reasoning.

thecatspjs

lilolil_1 wrote: »

Have work out to be 5.82mins? Am i right?

I don't think that's correct. It can't be less than 6 minutes if the boat has to alter it's course after that amount of time.
Draw a labelled diagram (as accurate and to scale as possible) and have another think about it. What would be a reasonable answer in your opinion? It takes a few trigonometric relations to calculate the answer, but if you have an idea of what it should be you'll be on the right track.

lilolil_1

just looking at the answer i used 4 minutes instead of 6 minutes for the first leg of the journey! will re-do now! will post then!

lilolil_1

ans is 7.52 minutes! sorry! used the 6minutes in my original calculation but added on 4 minutes at the end!

Morbert

I get 7 minutes 19 seconds (roughly).

After the 6 minutes, I have the boat at (1527.35,1527.35). Which only is a distance of 708 m from the buoy, which the boat can travel in approx 79 seconds if it is travelling at 9m/s.

lilolil_1

leave it with me. babies screaming here. all goin to bed and i'll redo!

lilolil_1

Morbet - Got the same! yahoo! and i did it mostly on my own! thanks a million! it was just a matter of finding the right triamgles to get the dimensions of! star - thank you!

lilolil_1

Theres another boat in the race! boat a - travelling leg 1 at a bearing of 30deg east of north for 6ms-1 for 4 minutes. turns immediately towards the buoy at 1000m east and 2000m north and travelling at 7ms-1. I get the time for boat a to be 11mins 28 seconds to get to the buoy... tell me i'm right please!!!!

thecatspjs

lilolil_1 wrote: »

Theres another boat in the race! boat a - travelling leg 1 at a bearing of 30deg east of north for 6ms-1 for 4 minutes. turns immediately towards the buoy at 1000m east and 2000m north and travelling at 7ms-1. I get the time for boat a to be 11mins 28 seconds to get to the buoy... tell me i'm right please!!!!

Not what I'm getting. How did you come to this answer?