tmua.me Extreme Set B Paper 1 · Question 17

A particle moves along a straight line. At time $t$ seconds, its signed displacement in metres from its starting point is

s(t)=t^3-6t^2+bt,\qquad 0\leq t\leq4,

where $b$ is a real constant.

It is given that $s(4)>0$ and that the total distance travelled during these four seconds is $3s(4)$ .

At what time does the particle first return to its starting point after $t=0$ ?

1

second

\dfrac32

seconds

2

seconds

\dfrac83

seconds

3

seconds

FThere is no return for

0<t\leq4

examday