Recent content by Maianbarian

Ah, I get it now. We know that r(t).r(t)=|r(t)|^2. Differentiating the dot product we get: d/dt [r(t).r(t)]= 2r'(t).r(t) = 0 (as r'(t) is orthogonal to r(t)) thus |r(t)|^2 is constant, and so |r(t)| is constant, which corresponds to a sphere with the centre at the origin. Thanks Dick :)

Homework Statement If a curve has the property that the position vector r(t) is always perpendicular to the tangent vector r'(t) show that the curve lies on a sphere with center at the origin Homework Equations The Attempt at a Solution I have no idea how to even approach this...

Homework Statement A projectile is fired from the origin down an inclined plane that makes an angle theta with the horizontal. The projectile is launched at an angle alpha to the horizontal with an initial velocity v. Show that the angle of elevation alpha that will maximise the the...