Answer:
m = 5 [mg]
Explanation:
We must remember that the definition of linear momemtum is defined as the product of mass by distance.
P = m*v
P = momentum = 40 [mg*m/s]
m = mass [mg]
v = velocity = 8 [m/s]
Now clearing m:
m = P/v
m = 40/8
m = 5 [mg]
Since the two taped poles of the magnets labeled A and B attracts one to each other, we know that the two taped poles are oppsosite.
So, you can predict with total certainty that when she brings the taped end of the third magnet (magnet C) near each of the first two magntes, in one case they will attract each other and in the other case they will repele mutually.
You are certain of that because, since the taped poles of the first two magnets are opposite, the pole of the third magnet has to be equal to one of the two first taped poles and opposite to the other of the two firest taped poles.
(a) 
The change in energy of the transferred charge is given by:
where
q is the charge transferred
is the potential difference between the ground and the clouds
Here we have
So the change in energy is
(b) 7921 m/s
If the energy released is used to accelerate the car from rest, than its final kinetic energy would be
where
m = 950 kg is the mass of the car
v is the final speed of the car
Here the energy given to the car is
Therefore by re-arranging the equation, we find the final speed of the car:
I think the answer would be letter B.
