Answer:
A) F=-20.16×10⁹N
B) if the distance doubles, force is 4 times smaller.
Explanation:
q1=-28C
q2=5mC=0.005C
d=25cm=0.25m
Electrostatic force between charges: F=k×q1×q2/d², where k is a coefficient that has the value k=9 × 10⁹ N⋅m²⋅C^(-2) for air.
Thus:
F=9×10⁹×(-28)×0.005/0.25²
F=-20.16×10⁹N
The minus sign indicates attraction.
If distance doubles, d1=2×d, then we have 4d² at the denominator and the force is 4 times smaller.
Gravitational potential energy = mass × gravity × height
Ep = (4)(9.81)(3)
Energy = 117.72 Joules
= 1.2x10^2 Joules
Answer:
Part a)

Part b)

Part c)

Explanation:
Part a)
Moment of inertia of the system about an axis passing through B and C is given as




Part b)
Moment of inertia of the system about an axis passing through A and C is given as




Part c)
Moment of inertia of the system about an axis passing through the center of the square and perpendicular to the plane of the square




The doppler effect is the increase or decrease in the frequency of sound, light, or other waves as the source and observer move toward or away from each other.