This question is in two parts. Part 1 is about collisions. Part 2 is about the gravitational field of Mars.
## Part 1 Collisions
The experiment is repeated with the clay block placed at the edge of the table so that it is fired away from the table. The initial speed of the clay block is 4.3 m s−1 horizontally. The table surface is 0.85 m above the ground.
7a. (i) Ignoring air resistance, calculate the horizontal distance travelled by the clay block before it strikes the ground.
(ii) The diagram in (c) shows the path of the clay block neglecting air resistance. On the diagram, draw the approximate shape of the path that the clay block will take assuming that air resistance acts on the clay block.
## Part 2 Gravitational field of Mars
7b. Define *gravitational potential energy* of a mass at a point.
The graph shows the variation with distance r from the centre of Mars of the gravitational potential V. R is the radius of Mars which is 3.3 Mm. (Values of V for r<R are not shown.)
A rocket of mass 1.2×104 kg lifts off from the surface of Mars. Use the graph to
7c. (i) calculate the change in gravitational potential energy of the rocket at a distance 4R from the centre of Mars.
(ii) show that the magnitude of the gravitational field strength at a distance 4R from the centre of Mars is 0.23 N kg−1.