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)

Step-by-step 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 = (dD_x)/(dt) = -3 + 8t`

`a_x = (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

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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