Two ships moving one at 3i 4j km hr the other at 12i 5j km hr
This presentation is the property of its rightful owner.
Sponsored Links
1 / 8

Two Ships moving one at 3i+4j km/hr, the other at 12i-5j km/hr PowerPoint PPT Presentation


  • 87 Views
  • Uploaded on
  • Presentation posted in: General

Two Ships moving one at 3i+4j km/hr, the other at 12i-5j km/hr. Q) When will the ships be 20 km apart?. Step 1: Draw a diagram. Ship A. 3i+4j. Ship B. 12i-5j. After 1 hour, mark their positions. Ship A. 3i+4j. Ship B. 12i-5j.

Download Presentation

Two Ships moving one at 3i+4j km/hr, the other at 12i-5j km/hr

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Two ships moving one at 3i 4j km hr the other at 12i 5j km hr

Two Ships moving one at 3i+4j km/hr, the other at 12i-5j km/hr

Q) When will the ships be 20 km apart?


Step 1 draw a diagram

Step 1: Draw a diagram

Ship A

3i+4j

Ship B

12i-5j


After 1 hour mark their positions

After 1 hour, mark their positions

Ship A

3i+4j

Ship B

12i-5j

The length of the green line is the distance between both ships!


After 2 hour s mark their positions

After 2 hour’s, mark their positions

Ship A

3i+4j

The length of the green line is

again the distance between them

Ship B

12i-5j


Watching both ships in this manner it is difficult to determine when the green line is 20 km long

Watching both ships in this manner, it is difficult to determine when the green line is 20 km long.

  • A better method is to find the velocity of B relative to A, and to look at A on this diagram.

  • VA = 3i+4j

  • VB = 12i-5j

  • VBA = VB – VA = (12i-5j)-(3i+4j) = 9i-9j

  • This was the green line on the previous diagram


If the origin is at a and moving with a then the length of the green line is easy to find

If the origin is at A, and moving with A, then the length of the green line is easy to find.

Ship A

3i+4j

VBA = 9i-9j from Ship A

It is easier to draw a separate diagram to show the velocity of B relative to A, i.e., the green line above.

Ship B

12i-5j


Relative diagram

Relative Diagram

In this Diagram, Ship A is stationary and Ship B is moving at 9i-9j.

(In actual fact, the origin of this diagram is moving with Ship A, and the green line denotes the distance B is from A)

The speed of B relative to A is 12.7 km/hr.

So they will be 20 km apart after 20÷12.7 = 1.57 hrs = 1hr 34 mins.

VBA = 9i-9j

If you want to know how far A and B have moved from their starting points at this time, take this time back to the original diagram.


Two ships moving one at 3i 4j km hr the other at 12i 5j km hr

Ship A

3i+4j

The speed of ship A is 5 km/hr . After 1.57 hrs, Ship A has moved a distance of 5×1.57 = 7.85 km

The speed of Ship B is 13 km/hr . After 1.57 hrs, Ship B has moved a distance of 13×1.57 = 20.41 km

You should now use the Cosine rule

To confirm that the distance between

them is indeed 20 km.

Ship B

12i-5j


  • Login