Question

The displacement S of a body at instant t is S=2t^2+5t .If S and t are in metres.
Please solve the question ​

Answer 1

Answer:

Position is given as s = 2t^3 + t^2 + 6

So velocity, v, is ds/dt = 6t^2 + 2t

When v = 8.4m/s, 6t^2 + 2t = 8.4

Solving, t = 1.028

When v = 18m/s, 6t^2 + 2t = 18

Solving, t = 1.573

So s(8.4m/s) = 2(1.028^3) + 1.028^2 + 6 = 9.230m

So s(18m/s) = 2(1.573^3) + 1.573^2 + 6 = 16.259m

And Δs = 16.259 – 9.230 = 7.029m