Locus Question (1 Viewer)

[Aron]

Challenge Exercise 15

A satellite dish is to be 3.5m wide and 1.1m deep. Find the position of the focus in millimetres, correct to the nearest millimetre.

Thanks in advance =D

 

[carolineedwards]

Consider the dish to have vertex (0,0), hence the edge of the dish will have coordinates (1.75,1.1) as it is the width/2 and the given hight. Then you just substitute those values into the parabola equation x^2=4ay. And you get
(1.75)^2=4xax1.1
3.0625=4.4a
0.6960...=a

Therefore focus is 0.696 m (3dp) which equals 696mm

 

[leehuan]

This was asked in 2013

 

[braintic]

Where is it stated that this is a parabola?

 

[leehuan]

Where is it stated that this is a parabola?

From memory this was a MIF question under the locus topic so I think it was assumed.