Question

a horse starts from rest and speeds up with constant acceleration. If it has gone a distance of 100m at the point when it reaches a speed of 12m/s, what is its acceleration

Answer 1

Use \[v_f^2=v_i^2+2ad\]
\[v_f\] is your final velocity
\[v_i\] is your initial velocity
\[d\] is your distance
\[a\] is your acceleration

Now solve for a, note that the horse starts from rest which means your initial velocity = 0.