Answer:
E = 867 N/C, upward.
Explanation:
- Assuming no other forces acting on the particle, it must obey Newton's 2nd Law, as follows:
    [tex]F_{net} = m*a (1)[/tex]
- There are two forces acting on the particle in the vertical direction, one due to the electric field, and the other due to gravity.
- Since the particle is positively charged, assuming that the electric field aims upward, we can write the following expression for the left side of (1):
    [tex]F_{net} = q*E - m*g = m*a (2)[/tex]
- Since we know that q/m = 0.1 C/kg,
- ⇒ q = 0.1m C/kg
- Replacing this value of q in (2), and simplifying masses, we get:
    [tex]F_{net} = 0.1 *E - 9.8 m/s2 = a (3)[/tex]
- We can find the value of a, simply applying the definition of acceleration:
    [tex]a =\frac{\Delta v}{\Delta t} = \frac{200m/s}{2.6s} =76.9 m/s2 (4)[/tex]
- Replacing (4) in (3) and solving for E, we get:
- E = 867.2 N/C, upward.