the length of a chord of the parabola x^2=4ay passing through the vertex and having slope tanA is?

let a point on parabola be 2at,at^2. its vertex is the origin. the slope of chord is given by (at^2-0)/(2at-0)=tanA, implies t=2*tanA. length of chord is the distance between origin and the point of intersection i.e sq.root({at^2}^2+{2at}^2). substitute value of t to get answer to be 4asecAtanA.

a particle of mass 1 kg and carrying 0.01C is at rest on a inclined plane of angle 30 degrees with the horizontal when an electric field of 490/sq root(3) N/C applied parallel to the horizontal,the coefficient of friction is?