Physics for Scientists and Engineers 3rd Edition by Randall Knight, Chapter 1 Conceptual Question 5


Does the object represented in Figure Q1.5 have a positive or negative value of \displaystyle a_y? Explain.

Physics for Scientists and Engineers 3rd Edition by Randall Knight, Chapter 1 Conceptual Question 5

Figure Q1.5


Solution:

Because the velocity vectors get shorter for each time step, the object must be slowing down as it travels in the negative y (\displaystyle -y) direction (down). The acceleration vector must therefore point in the direction opposite to the velocity; namely, in the +y direction (up). Thus, \displaystyle a_y is positive as per the convention in the book. 


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