Question

If the displacement of an object is given in SI units by Dx = -3 t + 4 t 2, at t = 2 s its velocity and acceleration are, respectively:


a) positive, positive.


b) negative, positive.


c) negative, negative.


d) positive, negative.

Answer 1

(A)

Explanation:

If the displacement is given by

$D_x = -3t + 4t^2$

Then its velocity $v_x$ and acceleration $a_x$ are then

$v_x = \dfrac{dD_x}{dt} = -3 + 8t$

$a_x = \dfrac{dv_x}{dt} = 8$

Evaluated at t = 2, we see that $v_x = 13$ and $a_x = 8$ and both of them are positive. Therefore, the answer (a).

Answer 2

Answer:

QUESTION

If the displacement of an object is given in SI units by Dx = -3 t + 4 t 2, at t = 2 s its velocity and acceleration are, respectively:

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ANSWER

a) positive, positive

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