# The blades of a helicopter exert an upward force of 25,000 Newtons.  The mass of the helicopter is 2,000 kg.  What is the acceleration of the helicopter?

Use newtons second law where a force downward is negative and upward is positive.

Newtons second law is:

`F_(n e t)=sum_i F_i=m a`

Which just says the sum of the net force is equal to the sum of the individual forces thats equal to the mass times the acceleration.

Now...

Use newtons second law where a force downward is negative and upward is positive.

Newtons second law is:

`F_(n e t)=sum_i F_i=m a`

Which just says the sum of the net force is equal to the sum of the individual forces thats equal to the mass times the acceleration.

Now let `F_h` be the upward for due to the helicopter and `F_g` be due to gravity. Then we know:

`F_(n e t) =F_h-F_g=F_h-mg=ma`

Solve for a.

`(F_h-mg)/m=a`

Plug in the values and let the acceration for gravity g be 10 m/s/s.

`(25,000 N-2,000 kg *10 m/s^2)/(2,000 kg)=a`

`(25,000 N-2,000 kg *10 m/s^2)/(2,000 kg)=a`

`(25,000 N-20,000 N)/(2000 kg)=a`

`(5,000 N)/(2,000 kg)=a`

`5/3 (m/s^2) =a`

Therefore the acceleration of the helicopter is 5/3 meters per second per second upwards.

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