An object moves along a straight line so that at any time t , for 0≤t≤8 , its position is given by x(t)=5+4t−t2 . For what value

Question

3 years ago

15

of t is the object at rest?
A. t = 2
B. t = 4
C. t = 9/2
D. t = 5

2 answers:

saul85 [17] · Answer 1 · 2022-02-26T14:18:07+03:00

8 0

It’s ccccccccccccccccccccccc

olganol [36] · Answer 2 · 2022-02-26T15:51:26+03:00

4 0

Answer:

D. t = 5

when the object is at rest => x(t) = 0

<=> -t^2 + 4t + 5 = 0

<=> t^2 - 4t - 5 = 0

<=> (t - 5)(t + 1) = 0

=> t = 5 or t = -1

but t》0

=> t = 5