A rocket of mass m is lifting off of the surface of Earth with an acceleration equal to 3g. The force produced by the rockets thrust equ....?
equals

a) 1mg
b) 2mg
c) 3mg
d) 4mg
e) 5mg
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answers:
oubaas say: Thrust T = m(3g+g) = 4mg N ( this is necessary for overcoming the gravitational acceleration g)
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derfram say: 3mg.

If the thrust were 1mg, the rocket would sit on the pad, and an astronaut would feel 1g from the local gravitational field. If the thrust were 2mg, the rocket would accelerate upward at 1g, and the astronaut would feel 2g (1 g accel + 1g local). If the thrust were 3 mg, the rocket would accelerate upward at 2g, and the astronaut would feel 3g (2g accel + 1g local). So 3mg.
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Andrew Smith say: 4mg
The rocket requires a force of mg to stay still.
Then it requires a force of 3mg to accelerate upwards.

ie net force = ma = 3mg
but net force = applied force + gravitational force
3mg = applied force +(- mg)
4mg =applied force
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fzlvt say: czbwkspx
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