VCAA Physics How do things move without contact?

The satellite has inertia and, in the absence of the planet, would continue in a straight line with the same speed until acted upon by an unbalanced force.

When the planet's gravitational force pulls the satellite towards it (perpendicular to the satellite's motion), the satellite changes direction and thus accelerates towards the planet, but its speed does not change.

As a result, the satellite continues to move ‘forward’, but the planet’s gravitational force pulls the satellite towards it. So the resultant motion is that the satellite has a constant speed (not velocity as direction is changing) travelling in a circle around the planet.

$F = \frac{1}{4\pi\epsilon_0} \frac{Qq}{r^2}$
$0.025 = \frac{9 \times 10^9 \times Q^2}{0.30^2}$
$Q = \sqrt{\frac{0.025 \times 0.30^2}{9 \times 10^9}}$
$= 5.0 \times 10^{-7}$
Charge = $5.0 \times 10^{-7} \text{ C}$

$F = \frac{GMm}{r^2}$
$3.3 \times 10^3 = \frac{6.67 \times 10^{-11} \times 2.7 \times 10^{17} \times 6.1 \times 10^{15}}{r^2}$
$r = \sqrt{\frac{6.67 \times 10^{-11} \times 2.7 \times 10^{17} \times 6.1 \times 10^{15}}{3.3 \times 10^3}}$
$= 5.8 \times 10^9\ m$

Distance between asteroids = $5.8 \times 10^9$ m (to two significant figures)