What time t does the particle first cross the x axis?

AI Thread Summary
To determine when the particle first crosses the x-axis, the initial position is given as (4 m)j, and the initial velocity is (2 m/s)i, with a constant acceleration of -(2 m/s²)(i+j). The particle crosses the x-axis when its y-coordinate becomes zero, which can be calculated using kinematic equations. The discussion also addresses the need to understand the vector components represented by i and j, which denote the x and y directions, respectively. Clarification on the equations of motion and vector representation is essential for solving the problem effectively.
gap0063
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1.
(a) A particle has ~r(0) = (4 m)j and ~v(0) =
(2 m/s)i.
If its acceleration is constant and given by
~a = −(2 m/s2) (i+j), at what time t does the
particle first cross the x axis?
Answer in units of s.

(b) At what time t is the particle moving parallel to the y axis; that is, in the j direction
Answer in units of s




2.Some equation with a constant acceleration... not sure which one



3. I tired to draw it out but I don't know how... I don't understand how to start the problem
 
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Do you know what those i and j are?

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