Question

a bob of pendulum of mass 40mg a charge q 1uC is given to it length of pendulum is 90cm​

Answer 1

Explanation:

The mass of bob is m=40g

The charge on the bob is q=4×10

−6

C

Time for 20 oscillations=45sec.

Time for 1 oscillation =

20

45

sec

When no electric field is applied, the time period of oscillation is:

T=2π

g

l

⇒

20

45

=2π

10

l

⇒

10

l

=(

20

45

)

2

×

4π

2

1

⇒l=

(20)

2

×4π

2

(45)

2

×10

⇒l=

(20)

2

×4π

2

(45)

2

×10

1.2836