Kepler's Second Law of planetary motion (Law of Areas) is a direct consequence of the conservation of:
A. Total Mechanical Energy
B. Kinetic Energy
C. Linear Momentum
D. Angular Momentum
Answer: Option D
Solution (By JKSSB Mock Tests)
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.
Explanation:
In Einstein's photoelectric theory, electrons are bound to the metal lattice. The 'work function' (often denoted by Phi or W) is defined strictly as the absolute minimum thermodynamic work (energy) needed to overcome these binding forces and remove an electron from the surface into a vacuum. If incident photon energy (hf) is less than the work function, absolutely no emission occurs.
Explanation:
In non-uniform circular motion, the speed of the particle changes. This requires a tangential acceleration (at) to change the speed, and a centripetal/radial acceleration (ac) to change the direction. The net acceleration is the vector sum of these two mutually perpendicular components, so it points inward at an angle to the radius.
No comments yet. Be the first to start the discussion!