Planets go around the sun in elliptical orbits.The highly exaggerated diagram below shows a portion of such an orbit and the force on the planet at one position along that orbit.The planet is moving to the right.F_|| and $\mathrm { F } _ { \perp }$ are the components of the force parallel (tangential)and perpendicular (normal)to the orbit.The work they do is W_|| and $W _ { \perp }$ .At the position shown A)W_|| slows the planet down; $W _ { \perp }$ speeds it up. B)W_|| slows the planet down; $W _ { \perp }$ does no work on it. C)W_|| speeds the planet up; $W _ { \perp }$ does no work on it. D)W_|| speeds the planet up; $W _ { \perp }$ slows it down. E)W_|| does no work on it; $W _ { \perp }$ speeds the planet up.

Question

Quizplus · Accepted Answer

At the position shown in the diagram, the force component parallel to the orbit (W_||) is opposite to the direction of motion of the planet, so it does work to slow the planet down. On the other hand, the force component perpendicular to the orbit (11ea99f6_d742_df77_8bb6_ede1a25120c6_TB5764_11_TB5764_11_TB5764_11_TB5764_11_TB5764_11_TB5764_11_TB5764_11_TB5764_11) is perpendicular to the direction of motion, so it does not do any work on the planet.

Planets Go Around the Sun in Elliptical Orbits F⊥\mathrm { F } _ { \perp }F⊥​

Planets Go Around the Sun in Elliptical Orbits $\mathrm { F } _ { \perp }$