Which scientific instrument is used specifically for measuring very high temperatures, such as the surface temperature of the Sun or inside a furnace, from a distance? MCQ with Answer and Explanation

Explanation:
Mass is constant, weight changes. 60 kg mass, weight 588 N on Earth, 98 N on moon.

Explanation:
In uniform circular motion, speed is constant but velocity direction changes continuously, requiring centripetal acceleration directed toward the center (a = v²/r). By Newton's second law, a centripetal force must act. Velocity isn't constant (direction changes); acceleration isn't zero; force is required. Memory tip: 'Uniform circular motion: constant speed, changing velocity, center-seeking acceleration'. This conceptual question tests understanding of circular dynamics, crucial for mechanics in competitive exams. Always distinguish speed (scalar) from velocity (vector) in motion analysis.

Explanation:
Kepler's Third Law (Law of Periods) states that the square of the time period (T^2) of any planet is proportional to the cube of the semi-major axis (r^3) of its orbit. Mathematically, T^2 is proportional to r^3. This law helps in calculating orbital periods or distances of planets and satellites.