A block of mass 5 kg is pushed against a wall with a horizontal force of 50 N. Coefficient of friction 0.4. The block (g=10) MCQ with Answer and Explanation

Explanation:
Fission: heavy nucleus (e.g., U-235) splits into smaller nuclei plus neutrons and energy. Fusion: light nuclei combine (e.g., hydrogen to helium). Both release energy. Fission used in reactors and bombs.

Explanation:
Carnot efficiency η = 1 - T₂/T₁, depending solely on absolute temperatures of heat source (T₁) and sink (T₂). It is independent of working substance, engine size, or other details. This universality makes Carnot cycle the theoretical maximum efficiency benchmark. Memory tip: 'Carnot efficiency: only T_hot and T_cold matter; real engines have lower efficiency'. This thermodynamics concept is frequently tested in competitive exams. Always recall that Carnot efficiency is an ideal limit; real engines have additional losses reducing efficiency below this value.

Explanation:
Kepler's Second Law states that the line joining a planet to the Sun sweeps out equal areas in equal intervals of time (areal velocity is constant). Because the gravitational force is a central force (acting strictly along the radius vector), it exerts zero torque on the planet. When net torque is zero, angular momentum is strictly conserved.