(i) In order to protect the ship from rough weather, the captain decided to slow it down. So he dropped the storm jib and lashed heavy mooring rope in a loop across the stern. Then they double-fastened everything and went through their life-raft drill. They also attached lifelines and wore life jackets. Thus, they got ready to face the storm.
(ii) To check the flooding of water in the ship, he took a canvas and stretched it across the holes, and made a waterproof hatch cover across the gaping holes which diverted the water to the side. When the two hands pump blocked and the electric pump short-circuited, he found another electric pump, connected it to an out pipe, and started it.
airship flagship lightship |
take on sth: | to begin to have a particular quality or appearance; to assume sth |
take sb on: | to employ sb; to engage sb to accept sb as one’s opponent in a game, contest or conflict |
take sb/sth on: | to decide to do sth; to allow sth/sb to enter e.g. a bus, plane or ship; to take sth/sb on board |
Temperature | Pressure thermometer A | Pressure thermometer B |
Triple-point of water | 1.250 × 10\(^5\) Pa | 0.200 × 10\(^5\) Pa |
Normal melting point of sulphur | 1.797× 10\(^5\) Pa | 0.287 × 10\(^5\) Pa |
Answer the following :
(a) The casing of a rocket in flight burns up due to friction. At whose expense is the heat energy required for burning obtained? The rocket or the atmosphere?
(b) Comets move around the sun in highly elliptical orbits. The gravitational force on the comet due to the sun is not normal to the comet’s velocity in general. Yet the work done by the gravitational force over every complete orbit of the comet is zero. Why ?
(c) An artificial satellite orbiting the earth in very thin atmosphere loses its energy gradually due to dissipation against atmospheric resistance, however small. Why then does its speed increase progressively as it comes closer and closer to the earth ?
(d) In Fig. 5.13(i) the man walks 2 m carrying a mass of 15 kg on his hands. In Fig. 5.13(ii), he walks the same distance pulling the rope behind him. The rope goes over a pulley, and a mass of 15 kg hangs at its other end. In which case is the work done greater ?