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A stone is thrown vertically upward and distance, S metre...

A stone is thrown vertically upward and distance, S metres after t seconds is given by S = 12t + 52t2 - t3.

Calculate the distance travelled in the third second.

A.

5.5m

B.

14.5m

C.

26.0m

D.

30.0m

Correct answer is A

From  S = 12t + 52t2 - t3;

Distance traveled in 2 seconds

 S = 12[2] + 52[2]2 - 23.

= 24 + 10 - 8 = 26m

Distance traveled in 3 seconds

 S = 12[3] + 52[3]2 - 33

= 36 + 22.5 - 27 = 31.5m

Distance traveled in the 3rd second

= 31.5m - 26m

: S = 5.5m