the acceleration formula goes like this: a= (vf-vi)/t so it would be (13-4)/3 thus the answer is 3m/s^2
3 is b my dude and the reason nobody answered is because thousands of questions are asked every day. so not every question can be answered. it doesn't have to do with being lazy.
the ultimate energy source for wind comes from earth's uneven heating on earth's surface which can be caused mainly by the sun.
apply newton's second law:
f = ma
m = 2kg
f = 4n
substitute the terms in the equation with the given values and solve for a:
4 = 2aa = 2m/s²