2020年10月IB物理(SL)真题PDF下载-paper2
1. A company delivers packages to customers using a small unmanned aircraft. Rotating horizontal blades exert a force on the surrounding air. The air above the aircraft is initially stationary.
The air is propelled vertically downwards with speed v. The aircraft hovers motionless above the ground. A package is suspended from the aircraft on a string. The mass of the aircraft is 0.95 kg and the combined mass of the package and string is 0.45 kg. The mass of air pushed downwards by the blades in one second is 1.7 kg.
(a) (i) State the value of the resultant force on the aircraft when hovering.
(ii) Outline, by reference to Newton’s third law, how the upward lift force on the aircraft is achieved.
(iii) Determine ν. State your answer to an appropriate number of significant figures.
(b) The package and string are now released and fall to the ground. The lift force on the aircraft remains unchanged. Calculate the initial acceleration of the aircraft.
2. The Rotor is an amusement park ride that can be modelled as a vertical cylinder of inner radius R rotating about its axis. When the cylinder rotates sufficiently fast, the floor drops out and the passengers stay motionless against the inner surface of the cylinder. The diagram shows a person taking the Rotor ride. The floor of the Rotor has been lowered away from the person.
(a) Draw and label the free-body diagram for the person.
(b) The person must not slide down the wall. Show that the minimum angular velocity ω of the cylinder for this situation is
ω=√g/µR
where μ is the coefficient of static friction between the person and the cylinder.
(c) The coefficient of static friction between the person and the cylinder is 0.40. The radius of the cylinder is 3.5 m. The cylinder makes 28 revolutions per minute. Deduce whether the person will slide down the inner surface of the cylinder.
2020年10月IB物理(SL)真题余下省略！
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