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# Mechanics past paper question watch

1. question 3 from Jan 2005 OCR paper M1:

Three coplanar forces of magnitudes 5 N, 8 N and 8 N act at the origin O of rectangular coordinate axes. The directions of the forces are as shown in the diagram.
(i) Find the component of the resultant of the three forces in
(a) the x-direction =10.6 N
(b) the y-direction = 3.83N
(ii) Find the magnitude and direction of the resultant.
Magnitude = 11.3N

Mark scheme states"Direction is 19.8degrees anticlockwise from +ve x-axis"

How do i used the magnitude of 11.3 N to work out the 19.8 degrees?
2. (Original post by Chelsea12345)
question 3 from Jan 2005 OCR paper M1:

Three coplanar forces of magnitudes 5 N, 8 N and 8 N act at the origin O of rectangular coordinate axes. The directions of the forces are as shown in the diagram.
(i) Find the component of the resultant of the three forces in
(a) the x-direction =10.6 N
(b) the y-direction = 3.83N
(ii) Find the magnitude and direction of the resultant.
Magnitude = 11.3N

Mark scheme states"Direction is 19.8degrees anticlockwise from +ve x-axis"

How do i used the magnitude of 11.3 N to work out the 19.8 degrees?

Where is the diagram?
3. resolve the force into it's horizontal and vertical components and then use pythagoras.
Where is the diagram?
i couldn't include a picture but i have linked the paper here: it's question 3.

http://pmt.physicsandmathstutor.com/...20M1%20OCR.pdf
5. (Original post by Chelsea12345)
(a) the x-direction =10.6 N
(b) the y-direction = 3.83N
(ii) Find the magnitude and direction of the resultant.
Magnitude = 11.3N

Mark scheme states"Direction is 19.8degrees anticlockwise from +ve x-axis"

How do i used the magnitude of 11.3 N to work out the 19.8 degrees?
You don't use the magnitude. Draw a right-angled triangle with the x and y components as the perpendicular sides and mark the angle. Which trig function will allow you to calculate the angle?
6. (Original post by RogerOxon)
You don't use the magnitude. Draw a right-angled triangle with the x and y components as the perpendicular sides and mark the angle. Which trig function will allow you to calculate the angle?
I got the angle using T = O/A. I'm unsure about working out the bit in the mark scheme, where it states the direction is " anticlockwise from +ve x-axis"?
7. (Original post by Chelsea12345)
I got the angle using T = O/A. I'm unsure about working out the bit in the mark scheme, where it states the direction is " anticlockwise from +ve x-axis"?
You chose the (larger) x component as the adjacent and the y component as the opposite. Both are positive, so the angle will be anti-clockwise from the x axis. Sketch the triangle on the diagram and mark the angle if it's still not clear.
8. wouldn't it be clockwise if both values are positive from the axis?

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