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Newtons Second law (maths)

I have no idea wjat im foing wrong i also tried taking 9.8(gravity) frim 1.5 and still had the wrong answer. I'll post the question below appreciate any help

8ii)

Original post by A0W0N

8ii)

But gravity (weight) needs to be included.
What force beats gravity and produces a net upwards acceleration of 1.5?

Reply 3

simon0

Also show us what you got for question 8i and did you use the diagram to help you with question 8ii?

Reply 4

A0W0N

Original post by simon0

Also show us what you got for question 8i and did you use the diagram to help you with question 8ii?

im still confused i already tried 1000*(9.8-1.5) which didn't give 11300 which is the correct answer (checked answer)

Reply 5

mqb2766

The force F must be greater than gravity (it's weight), not less than.
When it equals gravity, the helicopter will hover. If it's less than gravity, the helicopter will descend. If it's greater than gravity, the helicopter will move up.

Reply 6

username5099800

Original post by A0W0N

8ii)

initially i got that as well but

when using F=ma, the question refers to the thrust as that causes the acceleration and not the resultant force

Rf= resultant force
T= thrust
W= weight = 1000g

Rf=m•a= 1000•1.5

and because the body moves upwards, thrust must be greater so the resultant force is given by minusing the weight from the thrust in

T-W = Rf

and from the formula above we know that Rf = 1500 N
and to find weight we simply substitue W=mg so W=1000•9.8

and in the end, by substituting, we get

T - (1000•9.8)=1500

so T = 1500 (1000•9.8)

which gives us Thrust =11300

in short this question asks us for the magnitude of independant forces, rather than the magnitude of the resultant force.

hope that helped

(edited 4 years ago)

Reply 7

simon0