3.1. Momentum and Newton’s laws of motion
A subsection of Physics, 9702, through 3. Dynamics
Listing 10 of 131 questions
A small remote-controlled model aircraft has two propellers, each of diameter 16 cm. is a side view of the aircraft when hovering. 16 cm 16 cm body of aircraft air speed 7.6 m s–1 air speed 7.6 m s–1 propeller propeller Air is propelled vertically downwards by each propeller so that the aircraft hovers at a fixed position. The density of the air is 1.2 kg m–3. Assume that the air from each propeller moves with a constant speed of 7.6 m s–1 in a uniform cylinder of diameter 16 cm. Also assume that the air above each propeller is stationary. Show that, in a time interval of 3.0 s, the mass of air propelled downwards by one propeller is 0.55 kg. Calculate: the increase in momentum of the mass of air in increase in momentum = N s the downward force exerted on this mass of air by the propeller. force = N State: the upward force acting on one propeller force = N the name of the law that explains the relationship between the force in and the force in . Determine the mass of the aircraft. mass = kg In order for the aircraft to hover at a very high altitude , the propellers must propel the air downwards with a greater speed than when the aircraft hovers at a low altitude. Suggest the reason for this. When the aircraft is hovering at a high altitude, an electric fault causes the propellers to stop rotating. The aircraft falls vertically downwards. When the aircraft reaches a constant speed of 22 m s–1, it emits sound of frequency 3.0 kHz from an alarm. The speed of the sound in the air is 340 m s–1. Determine the frequency of the sound heard by a person standing vertically below the falling aircraft. frequency = Hz
9702_w19_qp_21
THEORY
2019
Paper 2, Variant 1
View
Questions Discovered
131