Question

The locus of the middle points of chords of the parabola $${y^2} = 8x$$  drawn through the vertex is a parabola whose :

A. focus is $$\left( {2,\,0} \right)$$
B. latus rectum $$ = 8$$
C. focus is $$\left( {0,\,2} \right)$$
D. latus rectum $$ = 4$$  
Answer :   latus rectum $$ = 4$$
Solution :
If the middle point of a chord is $$\left( {\alpha ,\,\beta } \right)$$  then $$\alpha = \frac{{2{t^2} + 0}}{2},\,\,\beta = \frac{{4t + 0}}{2}$$
Eliminating $$t,\,\alpha = {\left( {\frac{\beta }{2}} \right)^2}.$$   So, the locus is $${y^2} = 4x.$$

Releted MCQ Question on
Geometry >> Parabola

Releted Question 1

Consider a circle with its centre lying on the focus of the parabola $${y^2} = 2px$$   such that it touches the directrix of the parabola. Then a point of intersection of the circle and parabola is-

A. $$\left( {\frac{p}{2},\,p} \right){\text{ or }}\left( {\frac{p}{2},\, - p} \right)$$
B. $$\left( {\frac{p}{2},\, - \frac{p}{2}} \right)$$
C. $$\left( { - \frac{p}{2},\,p} \right)$$
D. $$\left( { - \frac{p}{2},\, - \frac{p}{2}} \right)$$
Releted Question 2

The curve described parametrically by $$x = {t^2} + t + 1,\,\,y = {t^2} - t + 1$$      represents-

A. a pair of straight lines
B. an ellipse
C. a parabola
D. a hyperbola
Releted Question 3

If $$x+y=k$$   is normal to $${y^2} = 12x,$$   then $$k$$ is-

A. $$3$$
B. $$9$$
C. $$ - 9$$
D. $$ - 3$$
Releted Question 4

If the line $$x-1=0$$   is the directrix of the parabola $${y^2} - kx + 8 = 0,$$    then one of the values of $$k$$ is-

A. $$\frac{1}{8}$$
B. $$8$$
C. $$4$$
D. $$\frac{1}{4}$$

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Parabola


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