A space probe is descending vertically towards the surface of Mars to make a soft landing. At the instant shown (see diagram), when the probe is 400 m vertically above the surface, its speed is 40m/s. At this instant a metal object separates from the bottom of the space probe and falls freely under the influence of gravity on Mars. g on Mars may be taken as 4.0 m/s2. How long does it take in seconds for the free-falling metal object to reach the Martian surface?