M2

write F = q(v x B)

find direction of force , and also write F = mv²/r

so u get the r . now draw the circle . and u will find the answers

and yes, use te fact that velocity will be tangential or always _|_ to the radius of the circle . and by using some geometry, u can find the angle subtended by arc in terms of theta

a) mv/bq
(general formula by equating mv²/r=qvb

b) n-2@

c) arc in magnetic field=mvbqx n-2@

apply velocity=distance/time time= (mvbqx n-2@)/v

time= m(n-2@)/bq

d) replace - by + in b) and c) but a) remains same....