AP EAMCET Engineering 2018 Apr 22 Shift 1 Paper

The force experienced by an electric charge is given as,
F=qE
ma=qE
a=

qE

m

Substitute the values in above expression.
a=

2×10−6×4.2×104m∕s2

0.04

a=2.1m∕s2
The expression of time period in absence of an electric field is,
T0=2π√

l

g

=2π√

l

10

The expression of time period in presence of an electric field is,
T1=2π√

l

ae

=2π√

l

ae

=2π√

l

a+g

=2π√

l

12.1

Here, the effective acceleration on bob is ae
The ratio of time period is,

T0

T1

=√

12.1

10

=

11

10

T1=

10

11

×

44

20

=2s
The time taken to complete 15 oscillation is,
T1=2s×15=30s