Question

If and object accelerates from rest,with a constant acceleration of 5.4m/s2,what will its velocity be after 28s

Answer 1

"Acceleration of  5.4 m/s² " means that its speed increases by 5.4 m/s
every second.

If it starts from zero, then after 28 sec its speed is (28 x 5.4) = 151.2 m/s.