Physics GCSE question past paper velocity and momentum

Hi
Got my physics gcse tomoro :/ and i was just stuck on this question from a past paper.

There is a radio controlled flying toy. It is powered by a fan blade. It has a weight of 0.6N
When hovering in air, the fan pushes 1.5kg of air downwards every 10s. What is the velocity of the air when the toy is hovering?

the equations given are momentum=mass x velocity
and force = change in momentum/time taken

The answer is 4m/s (from the mark scheme). I figured that if you do (0.6/1.5) x 10 =4m/s
but can somebody explain how this works because I don't get how to solve this kind of question? :/

well, you know the force needed to hold up the flying toy (0.6N), and that the toy isn't moving up or down. So, we know that the force generated by pushing the air down is 0.6N, and the force on the air is 0.6N.


sooo
if
force = change in momentum/time taken
then
0.6N= change in momentum/10s (because it took 10 seconds)
so
0.6 x 10 = change in momentum
=6Ns (Newton Seconds) or Kg/s

and if
Momentum=mass x velocity
we're looking at ths over the period of 10 seconds, so we'd use the mass displaced in 10s
so
6 = 1.5 x velocity
soo
velocity = 6/1.5
=4M/s

Hope this helped and good luck

To hover the copter needs a rxn force=its weight=0.6N
Force exerted on air=F=ma=mdv/dt..NII..or F=rate of change of momentum
change of momentum of air =mv..F=mv/t=0.6
>1.5*v/10=0.6N..v=4m/s

i remember doing GCSE papers about 10 years ago.

Your exam is tomorrow - dont stress about little things like this now.

Remember that equation and just feel good about yourself.

Go into the exam and do your best

Good Luck!!!