Question

A particle is moving in a straight line and its distance s cm from a fixed point in the line after t seconds is given by s = 12t – 15t^2 + 4t^3. What is the velocity of the particle after 3 seconds?

(a) 10 cm/sec

(b) 20 cm/sec

(c) 30 cm/sec

(d) 40 cm/sec

The question was asked in class test.

I want to ask this question from Calculus Application topic in section Application of Calculus of Mathematics – Class 12

Answer 1

Correct option is (c) 30 cm/sec

To elaborate: We have, s = 12t – 15t^2 + 4t^3 ……….(1)

Differentiating both side of (1) with respect to t we get,

(ds/dt) = 12 – 30t + 12t^2

So, velocity of the particle after 3 seconds is,

[ds/dt]t = 3 = 12 – 30(3) + 12(3)^2

= 30 cm/sec.