Answer:
Q = -52.56 nC
Step-by-step explanation:
The electric field outside a spherical shell is given by
![E = (k*Q)/(r^(2) )](https://img.qammunity.org/2021/formulas/physics/high-school/h8zycnu6lacrv42yups670aix23huxah9e.png)
where:
Q is the net charge
r is the radius of the spherical shell and E is the electric field magnitude.
Given:
r = 0.725 m
since the field points radially toward the center of the sphere, E = -899 N/C.
k is a constant with a value = 8.99 x 109 Nm²/C².
∴
![-899 = (8.99*10^(9) *Q)/(0.725^(2) )](https://img.qammunity.org/2021/formulas/physics/high-school/owsccyvpqglo17nlpef6rzd9hx8vocoua6.png)
![Q = (-899*0.725^(2) )/(8.99*10^(9) )=-5.256*10^(-8)](https://img.qammunity.org/2021/formulas/physics/high-school/rr88p8tc0x2rxvam971xy5nuc929jwvwhl.png)
Q = -52.56 nC