A car is moving along a straight horizontal road, with a constant acceleration. The car passes point A, with a speed of ums(-1). 10 seconds later, passes point B, with a speed of 45 ms(-1). The distance from A to B is 300m. Find u.

Here, we must consider our UVAST equations of motion, and our variables.

U=?ms^(-1),  V=45ms^(-1) , A=?ms^(-2),   S= 300m,   T=10s

Our equations of motion are:

V = U + AT , S = (1/2)(V+U)T , S = UT + (1/2)AT^2 , V^2 = U^2 + 2AS

We know, V, S and T. And want to find U.

The right equation to find U is therefore ​S = (1/2)(V+U)T

Re-arranging we have: ((2)(S)/T ) - V = U

Therefore = ((2 * 300 ) / 10 ) - 45 = U

Therefore  U = 15ms^(-1)