Question

An object in orbit will have one of four shapes: circular, elliptical, parabolic or hyperbolic. Explain how you know that for the orbiting object ∑F ≠ 0.

Answer 1

the orbiting object is accelerating toward the centre of its orbit so in a Newtonian sense it must be experiencing a constant force acting toward that centre. in that sense, ∑F > 0.

to exalboate, velocity is a vector quantity so momentum is a vector too. a change in velocity can be a change in magnitude or a change in direction of the vector. it is the latter in a circular orbit, so the acceleration vector points towards the centre of orbit.

Answer 2

thank you