8 11 The International Space Station (ISS) orbits the Earth with a constant speed v. The orbit is circular and of radius r. (a) The diagram represents two positions, A and B, of ISS during its orbit. r A B v Draw a labelled vector diagram, in the space below, of the velocities at the two positions that shows the acceleration is directed towards the centre of the orbit. (2) Turn over 9 (b) (i) The ISS completes one orbit in 92 minutes. Calculate the centripetal acceleration of the ISS. r = 6800 km (3) ................................................................................................................................................................................................................................................... ................................................................................................................................................................................................................................................... ................................................................................................................................................................................................................................................... ................................................................................................................................................................................................................................................... ................................................................................................................................................................................................................................................... Centripetal acceleration = ....................................................... (ii) Astronauts in the ISS are often described as being “weightless”. Discuss whether the astronauts are “weightless” when they are orbiting the Earth in the ISS. (4) ................................................................................................................................................................................................................................................... ................................................................................................................................................................................................................................................... ................................................................................................................................................................................................................................................... ................................................................................................................................................................................................................................................... ................................................................................................................................................................................................................................................... ................................................................................................................................................................................................................................................... ................................................................................................................................................................................................................................................... ................................................................................................................................................................................................................................................... ................................................................................................................................................................................................................................................... (Total for Question 11 = 9 marks)