Question

δa is the area swept
δt is the time interval
kepler’s third law: this law states that the square of the time period (p) is directly proportional to the cube of the semi - major axis of its orbit.
p² ∝ a³
1: when a planet orbits the sun, one of the foci of the elliptical orbit is
a. the axis b. the perihelion c. the centre d. the sun

Explanation:

Kepler's laws of planetary motion state that planets move in elliptical orbits with the Sun at one of the foci. So for a planet orbiting the Sun, one focus of the elliptical orbit is the Sun. Option a (The axis) is incorrect as axis is not a focus. Option b (The perihelion) is the closest point to the Sun, not a focus. Option c (The centre) is incorrect as the center of the ellipse is not a focus (foci are inside the ellipse, and for planetary orbits, Sun is at a focus).

Answer:

d. The Sun