Shape and space – part 2
Reverse Bearings
It is possible to work out a bearing for your return journey just by calculation. You need to feel comfortable with angles and parallel lines to try it.
Example:
Kelly walks from X village to Y village on a bearing of 80°. Later she makes the return journey. What bearing does she need to take to get back from Y to X?
First draw a North line through Y
To find the bearing we face North and turn clockwise.
But this angle can be split into 2 parts
This part is 180° (straight line)
This part is 80° (alternate to 80° on the parallel North lines)
So the bearing of X from Y is 180° + 80°
= 260°
A)Try working out the bearing of A from B in these questions
1)2)
3)4)
5)6)
The calculation will be different if the outward bearing is more than 180°
The bearing of B from A is 280°
We need to find the bearing of A from B
(angle b)
The 280° bearing can be split into 2 parts again
This part is 180° as the angle is on a straight line
This part is 100° (280° - 180°)
So b will also equal 100° because it is alternate to 100°
The bearing of A from B is 100°
B)Try these questions:
Find the bearing of A from B
1)2)3)
4)5)6)
C)Try drawing a sketch to help you to answer these questions (as in question 1)
1)A rescue helicopter flies on a bearing of 125° to find a dinghy. On what bearing will it need to return to its base?
2)On the next day the helicopter is sent out to rescue a stranded bather on a bearing of 065°. On what bearing will it make the return journey?
3)The next day the helicopter rescues an injured climber on a bearing of 168°. What bearing will it need for the return journey?
4)At the weekend the crew are called out to pick up a fisherman in difficulties, on a bearing of 250°. What bearing will they return on?
Check your answers then discuss with your tutor what you need to work on next.
Answers
Reverse Bearings
A)
1)250°
2)220°
3)245°
4)325°
5)287°
6)352°
B)
1)050°
2)080°
3)110°
4)095°
5)130°
6)155°
C)
1)305°
2)245°
3)348°
4)070°
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