The radial force on the particle is given by the Lorentz force. They don't give you the velocity so you have to solve for it in terms of the radius and get them to cancel.
Physics is the study of matter and energy. Physics is also the study of how matter and energy interact.
Answer:
The planets formed due to dust and gases combination.The general theory of formation of sun is also same like planet they both are formed by the gases and dust particle.
Accretion is the presently accepted method by which planets are formed .Initially only formed planets were formed they are mars ,venus ,mercury and earth .So we can say that all planets were formed from gases and dust.
Since the current is inversely propotional to its resistance, when the voltage is doubled the current will be one-half