Here is a pretty straight forward question.
The only problem is, I got confused as to what happens with - and + numbers when they are squared etc...
Could anybody kindly guide me through the following problem and explain step by step what is taking place?
Ok here goes:
Q. A body is projected vertically upwards from ground level at a speed of 24.5ms-¹. Calculate the length of time that the stone is at least 19.6m above ground level.
I understand that if I use SUVAT, s = 19.6, u = 24.5, a = -9.8ms²
Therefore I must use: s = ut + 1/2 at²
Therefore: 19.6 = 24.5(t) + 1/2 -9.8(t²
Therefore: 19.6 = 24.5(t) + -4.9(t²
Therefore: ??? Now i'm unsure how to make t the subject, what happens with the +-4.9 ???