From where do we get v = u - gt?

Question

from where do we get v = u-gt

and what are the three laws of motion?

s = ut + .5at^2

v^2 = u^2 + 2as and

v = u - at
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please helpppppppppppppppppppp

Answer 1

From calculus. These results are derived by integrating Newton's law F=ma for the special case of a uniform force and, therefore, acceleration a. From its definition:
a=d^2s/dt^2 (the second derivative of distance s).
Integrating once gives you at+u=v, where v=ds/dt and u is the integration constant corresponding to its initial value. Integrating again, you get .5at^2+ut + s_0 = s where s_0 is the initial value of s. Your middle equation comes from solving both these equations for t and equating.

Answer 2

since gravity is negetive acceleration.
=> g = -a.
so substitute in the eqn.
also this is valid for motions that have a vertical component.

Answer 3

http://hyperphysics.phy-astr.gsu.edu/hbase/vel.html#velcon
Hyperphysics is the best physics site.