A particle with charge e and mass m, moving along the X-axis with a uniform speed u, enters a region where a uniform electric field E is acting along the Y-axis. The particle starts to move in a parabola. Its focal length (neglecting any effect of gravity) is

An electron enters an electric field having intensity $$E = 3\widehat i + 6\widehat j + 2\widehat k$$ Vm^$$-$$1 and magnetic field having induction $$B = 2\widehat i + 3\widehat j$$ T with a velocity $$v = 2\widehat i + 3\widehat j$$ ms^$$-$$1. The magnitude of the force acting on the electron is (Given, $$e = - 1.6 \times {10^{ - 19}}$$ C)