Answer:
2583.9 N/C
Explanation:
Parameters given:
Outer diameter = 14 cm
Outer radius, R = 7cm = 0.07m
Inner diameter = 7 cm
Inner radius, r = 3.5 cm = 0.035m
Charge of washer = 8 nC = 8 * 10^(-9)C
Distance from washer, z = 33 cm = 0.33m
The electric field due to a washer (hollow disk) is given as:
E = k * σ * 2π [ 1 - z/(√(z² + R²)]
Where σ = charge per unit area
σ = q/π(R² - r²)
σ = 8 * 10^(-9) /(π*(0.07 - 0.035)²)
σ = 2.077 * 10^(-6) C/m²
=> E = 9 * 10^9 * 2.077 * 10^(-6) * 2π * [1 - 0.33/(√(0.33² + 0.07²)]
E = 117.467 * 10^3 * (1 - 0.978)
E = 117.467 * 10^3 * 0.022
E = 2583.9 N/C
The period of a simple pendulum is given by:

where L is the pendulum length, and g is the gravitational acceleration of the planet. Re-arranging the formula, we get:

(1)
We already know the length of the pendulum, L=1.38 m, however we need to find its period of oscillation.
We know it makes N=441 oscillations in t=1090 s, therefore its frequency is

And its period is the reciprocal of its frequency:

So now we can use eq.(1) to find the gravitational acceleration of the planet:
Answer:
m = 3 kg
The mass m is 3 kg
Explanation:
From the equations of motion;
s = 0.5(u+v)t
Making t thr subject of formula;
t = 2s/(u+v)
t = time taken
s = distance travelled during deceleration = 62.5 m
u = initial speed = 25 m/s
v = final velocity = 0
Substituting the given values;
t = (2×62.5)/(25+0)
t = 5
Since, t = 5 the acceleration during this period is;
acceleration a = ∆v/t = (v-u)/t
a = (25)/5
a = 5 m/s^2
Force F = mass × acceleration
F = ma
Making m the subject of formula;
m = F/a
net force F = 15.0N
Substituting the values
m = 15/5
m = 3 kg
The mass m is 3 kg
density = mass/volume = 100kg/10ml = 10kg/ml
voluime = mass/density = 50g/2 g/ml = 25 ml
mass = density x volume = 2x55 = 110 kg