Question 18N.2.SL.TZ0.1d.ii
| Date | November 2018 | Marks available | [Maximum mark: 1] | Reference code | 18N.2.SL.TZ0.1d.ii |
| Level | SL | Paper | 2 | Time zone | TZ0 |
| Command term | Suggest | Question number | d.ii | Adapted from | N/A |
Ion-thrust engines can power spacecraft. In this type of engine, ions are created in a chamber and expelled from the spacecraft. The spacecraft is in outer space when the propulsion system is turned on. The spacecraft starts from rest.
The mass of ions ejected each second is 6.6 × 10–6 kg and the speed of each ion is 5.2 × 104 m s–1. The initial total mass of the spacecraft and its fuel is 740 kg. Assume that the ions travel away from the spacecraft parallel to its direction of motion.
An initial mass of 60 kg of fuel is in the spacecraft for a journey to a planet. Half of the fuel will be required to slow down the spacecraft before arrival at the destination planet.
In practice, the ions leave the spacecraft at a range of angles as shown.
On arrival at the planet, the spacecraft goes into orbit as it comes into the gravitational field of the planet.
Newton’s law of gravitation applies to point masses. Suggest why the law can be applied to a satellite orbiting a spherical planet of uniform density.
[1]
satellite has a much smaller mass/diameter/size than the planet «so approximates to a point mass» ✔
