Question

29. A 2 - gram object, located in a region of uniform electric field E = (300 N C) i carries a charge Q. The object released from rest at x = 0, has a kinetic energy of 0.12 J at x = 0.5 m. Then Q is (A) 400 uc (B) - 400 uc v (C) 800 με (D) - 800 uc 30. ​

Answer 1

Given:

A 2 - gram object, located in a region of uniform electric field E = (300 N C) i carries a charge Q. The object released from rest at x = 0, has a kinetic energy of 0.12 J at x = 0.5 m.

To find:

Value of charge?

Calculation:

In these type of questions, it is best to apply WORK-ENERGY THEOREM :

$\rm W_{net} = \Delta KE$

$\rm \implies force \times d = \Delta KE$

$\rm \implies EQ\times d = \Delta KE$

$\rm \implies EQ\times d = \dfrac{1}{2} m {v}^{2} - 0$

$\rm \implies 300Q\times 0.5 = 0.12 - 0$

$\rm \implies 300Q\times 0.5 = 0.12$

$\rm \implies Q= 800 \: \mu C$

So, value of charge is 800 micro-C.