Question

1. Give a short answer to the following questions. Please keep your reasoning to the point. (a) You put two identical glasses of water on a scale, both filled to the brim, but one with a piece of wood floating in it. Which one is heavier? (b) A particular cat likes to sleep on window sills. Today it falls from a particularly high one, finding itself in a perilous configuration with its legs upside down. By twisting its body in a special cat-like fashion, the cat rotates its body by 180° and manages to lands on its legs. Explain briefly how this can happen without contradicting the law of conservation of angular momentum. Ignore friction. (c) We all laugh when we read that the boastful Baron Münchausen is so strong that he dragged himself and his horse out of a swamp by pulling his own hair. But do n't a cyclist climbing onto a sidewalk act in the same way? Indeed when the front wheel of the bicycle approaches the sidewalk, one pulls up the handlebars, raising the front of the bicycle, thereby climbing onto the sidewalk without crashing. Why does the cyclist succeed while our friend Münchausen failed? Give reasons. (d) Your plane is on the runway, accelerating horizontally before takeoff. You notice that a freely hanging thread makes an angle of 5° from the vertical. Deduce the plane's acceleration (short calculation needed). (e) You are in the center of a 150m-long metro train (which has a single open interior, such as Montréal's Azur metro cars). It is off rush hour, and as the train accelerates to leave the station, you experience a sustained wind. Explain why that happens. Now suppose the train were hermetically sealed: do you think a sustained wind would be possible?

Answer 1

A Neither glass is heavier both weight the same. As both are lilled to the brim. The water displaced by the piece of I wood is equal to weight of water. & At all times the angular momentum of cat is zero. Cat on twisting sharply its body into divided into two half axes nullify the total angular momentum to zero. According to Newton's third law, every force has equal and opposite reaction. In our first case, the system is the person and the force applied by the person itself without any media involved. Therefore, total force is zero. while in case two, the system is bicycle and force applied by the person. Thus, there is some net finite force. ic masing ma cas 5o = mg a-yor = 9.8379 mis