Question

An electron of mass 0.90×10 power -30 kg under the action of a magnetic force moves in a circle of 2.0 cm radius at a speed of 3.0×10 power 6m/sec . if proton of mass 1.8×10 power -27 kg were to move in circle of the same radius and if it were acted upon by the same magnetic field then its speed will be (1)3.0×10 power 6 m/sec (2) 1.5× 10 power 3m/sec (3) 6×10 power 4m/sec (4) can not be estimated from given data