A ship entering a river from sea will MCQ with Answer and Explanation

Explanation:
Newton's Law of Universal Gravitation states that the gravitational force (F) between two point masses is directly proportional to the product of their masses (m1 × m2) and inversely proportional to the square of the distance (r²) between their centers. The mathematical formula is F = G(m1m2)/r².

Explanation:
Least count of screw gauge = Pitch / Number of circular scale divisions. Given pitch = 1 mm, divisions = 100, so LC = 1 mm / 100 = 0.01 mm. This represents the smallest measurement the instrument can accurately detect. Screw gauges measure small dimensions like wire diameter with high precision. Memory tip: Least count formula is universal for vernier and screw instruments: value per division on main scale divided by total circular divisions. This concept is frequently tested in practical physics sections of competitive exams.

Explanation:
Nucleus contains protons (positive) and neutrons (neutral), collectively nucleons. Electrons orbit nucleus. Atomic number Z = protons, mass number A = protons + neutrons. Isotopes differ in neutron number.