EAMCET Engineering 2007 Solved Paper

When a charged particle moves perpendicular to the magnetic field, it follows a circular path. On the circular path its velocity and acceleration will be at right angle to each other.
Given, ‌‌

→

v

=2

^

i

+c

^

j

,‌‌

→

a

=3

^

i

+4

^

j

As

→

v

and

→

a

are perpendicular, hence

→

v

⋅

→

a

=0
(2

^

i

+c

^

j

)⋅(3

^

i

+4

^

j

)=0⇒6+4c=0⇒c=−1.5