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electricsound
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1. The rotating blade of a hovering helicopter sweeps out an area of radius 4m imparting a downward velocity of 12ms^-1 to the air displaced. Find the mass of the helicopter.
(g=10ms^-2, density of air= 1.3 kgm^-3)
F=d/dt(mv)
F= (density of air*volume)*12
= 1.3*pie*16*12*12
=9409N
mass of helicopter= 940kg (the answers matched, but is it worked correct?)
2. The speed of rotation of the blades of the helicopter in question 1 is increased so that the air now hasa downward velocity of 13ms^-1. Find the upward acceleration of the helicopter.
attempt at the solution
F=mv
11043N=1.3(pie*16*13*13
F=ma
11043N=940*a
11043/940=a
Actual answer= 1.7ms^-2
(g=10ms^-2, density of air= 1.3 kgm^-3)
The Attempt at a Solution
F=d/dt(mv)
F= (density of air*volume)*12
= 1.3*pie*16*12*12
=9409N
mass of helicopter= 940kg (the answers matched, but is it worked correct?)
2. The speed of rotation of the blades of the helicopter in question 1 is increased so that the air now hasa downward velocity of 13ms^-1. Find the upward acceleration of the helicopter.
attempt at the solution
F=mv
11043N=1.3(pie*16*13*13
F=ma
11043N=940*a
11043/940=a
Actual answer= 1.7ms^-2