1) "Hot and cold". If fully opens cold water tap, a tub is filled in t 1 = 8 min. If placed at the exit of the key then shower hose with filling time increases to t 2 = 14 min. When the cold water tap is closed and fully open the hot water is filling time t 3 = 12 min, with shower hose and extends time t 4 = 18 min. How soon the tub was filled completely open if the two keys simultaneously without shower and then shower?
2) "Leaving the Moon." What part of a spaceship in circular orbit of radius 2R L around the Moon (Moon radius R L = 1.74 × 10 3 km) should be fuel, so as result of a short-ignition engine, you can leave the Earth's gravitational field? The exit velocity of the gas jet is u = 4 km / s. The acceleration of gravity at the surface of the moon is L g = 1.64 m / s 2.
3) "Injecting". Investigate factors that depend on the output rate of a liquid from a syringe with the force F applied to the plunger.
4) "Curiosa water pump." In the next figure shows a device used to raise water to a height h of a stream. K 1 and k 2 are two valves that open and close. Investigate factors that determines the amount of water that can be stored in a given time and explain the operating principle of said device
5) "Sifting water." The container has a number of very small holes in a base and depositing nevertheless this water to a certain height, the container empties no. To investigate this phenomenon
6) "artificial gravity." In a space station project aims to create an artificial gravity. Could be a cylinder of radius r = 300 m, rotating with an angular velocity w about the axial shaft linked with an inertial reference systemS.
a) What should be the angular velocity w for a body in the inner surface of the cylinder experiences a weight on the surface of the Earth?
b) If the station an object falls from a height h = 10 m
Describe qualitatively the motion of the object in the reference system S.
Determine the time required for the object arrives at the floor, or drop point. c) If the object is launched from a ground point with respect to the return on the floor:
Is there a time limit?
So that return to t = 2.5 s in which direction and how fast over the season should be released? 7) "Doing donuts." Have you noticed that when preparing donuts, sometimes when they are floating in oil begin to rotate at times significantly faster. Propose a theory to explain the rotation. Experiment if it thinks fit. 8) "Freedom". Proposes interesting experimental problem and solve it.
9) "Tube" U "spinning." In a U-shaped tube are poured two immiscible liquids whose densities relate as 2:1. While the tube is stationary, the area of separation of the liquid passing through the axis of symmetry of the tube. Whither moves and how much the surface of separation if the tube is rotated with respect to the
symmetry axis with angular velocity w = 5 s -1?
10) "Helicopter pedal." Someone built a pedal helicopter propeller low mass and diameter d = 8 m. Can a pilot mass M = 80 kg take off on that device?
Physical Futures Tournament VI 1998
1 "starting to fly." Early balloons or dirigibles aerostatic were inflated with hydrogen. During the First World War these airships were an easy target as a projectile however small were burnt, thus disappeared from the battlefield.
But one day in 1918 over the skies of London received an airship appeared many impacts without fire or fall to the ground, had been inflated with helium. But someone said: "The density of helium is nearly twice that of hydrogen, therefore the lift force of the balloon must be halved." Is this correct? Fundamente.
2 "A paradox." A bogie which has the shape shown in the figure is filled with water. Average pressures on the front and rear walls are equal, since only depend on the height of the liquid column and density. The front wall being larger than the rear area, should also be higher than the fluid force exerted forwards than backwards and exerts itself wagon should move forwards. Where is the error of this reasoning? Fundamente.
3 "playing pool". They are fashionable billiard tables whose edges are heated. What is the benefit? How does this benefit depends on temperature? 4 "Do not panic." Lately there has been speculation about the possibility of an asteroid hitting earth. Describe what would happen if an asteroid 10 km in diameter and density of the Earth collided with the earth.
5 "Resources housewives." Without breaking it is possible to determine if a chicken egg is raw or cooked. Exposing its corresponding theory.
6 "Move granted." Sit in a chair on a fairly smooth surface. Stretching strong feet and then gently picking them up you can move from corner to corner of the room. Apparently this violates the principle that a system can not propel yourself and external force required to accelerate. Since no external force applied on you how does it move? How do you resolve this paradox?
7 "Speaking of football." Estimate the speed with which you can kick a soccer ball. Will there be a maximum limit speed with which to shoot a penalty kick?
8 "Tennis Shoes". Tennis shoes must have certain features such as allowing a rapid increase in speed or braking sharply to a basketball player, which can be determined by the coefficients of static and kinetic friction of such shoes. Measure friction coefficients of different tennis shoes. Do you agree with this there is the maximum speed limit at which an athlete can move forward?