Both Coulomb's law (electric) and Newton's law of gravitation have inverse-square distance dependence. A key difference is:
A.
Gravitational force obeys superposition; Coulomb force does not
B.
Gravitational force is always attractive; Coulomb force can be both attractive (unlike charges) and repulsive (like charges) — this allows partial or complete cancellation of electric forces
C.
Gravitational force is stronger than Coulomb force at large distances
D.
Coulomb force has infinite range; gravitational force has finite range
B. Gravitational force is always attractive; Coulomb force can be both attractive (unlike charges) and repulsive (like charges) — this allows partial or complete cancellation of electric forces
14.
The acceleration of an electron placed 1 Å (= 10⁻¹⁰ m) from a proton due to their mutual Coulomb attraction is approximately:
A.
aₑ ≈ 1.4 × 10¹⁹ m/s²
B.
aₑ ≈ 2.5 × 10¹² m/s²
C.
aₑ ≈ 9.8 m/s² — equal to gravitational acceleration
D.
aₑ ≈ 2.5 × 10²² m/s² — vastly larger than g = 9.8 m/s², so gravity is negligible
The electrostatic force between two charges is 0.2 N when separated by some distance r. When the separation is increased by 50% (to 1.5r), the force becomes:
A small charged sphere of charge 0.4 μC is placed in air near another sphere of charge −0.8 μC. The force between them is 0.2 N. The distance between them is:
