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# Vectors and scalars question need help Watch

1. Using the parallelogram method find the resultant vector : a boat travelling at 100km/h at a bearing of 90 degrees while the river current is 5km/h at a bearing of 170 degrees.
Thanks
2. Here is a draft, make sure you select a correct scale, e.g 1cm : 10 km/hr, and measure the angle using a protractor.
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3. (Original post by Fysiika07)
Here is a draft, make sure you select a correct scale, e.g 1cm : 10 km/hr, and measure the angle using a protractor.
Could you explain how you got to this draft?
4. The longer and horizontal arrow represent the vector of the boat's velocity. Place the tail of shorter arrow (vector of the current) at the head of the longer arrow. Then draw the dotted lines to form a parallelogram. Lastly the connect the corners, ie the resultant vector.
5. (Original post by Fysiika07)
The longer and horizontal arrow represent the vector of the boat's velocity. Place the tail of shorter arrow (vector of the current) at the head of the longer arrow. Then draw the dotted lines to form a parallelogram. Lastly the connect the corners, ie the resultant vector.
How do you workout the resultant vector from there?Cosine rule? And what about the angles?
6. (Original post by TheRanBoy)
How do you workout the resultant vector from there?Cosine rule? And what about the angles?
I supposed the question expects a proper scale for the diagram. Then, you just need to measure the length of the resultant, convert it using the scale to get the magnitude. Measure the angle from the horizontal vector (the velocity) using a protractor, add 90 deg to it, it will be the bearing.
7. (Original post by Fysiika07)
I supposed the question expects a proper scale for the diagram. Then, you just need to measure the length of the resultant, convert it using the scale to get the magnitude. Measure the angle from the horizontal vector (the velocity) using a protractor, add 90 deg to it, it will be the bearing.
8. (Original post by TheRanBoy)

magnitude: 120, bearing: 93

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