EK 1001 Physics #61

[justphuta]

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Hey everyone!
Just quick question..
a particle moving at 10m/s reverses its direction to move 20 in the opp. direction. If its acc is -10 m/s2, what is the total distance that it travels?

a. 15 meters
b. 20
c.25
d.30

i originally chose A, using the equation: v^2=v^2 +2ax, and solving for x.
After reading the explanation, i understood how they arrived to the correct answer, C.
any tips on when i can know when not to use this equation? seems to me that all the variables are in place and should work too. THANKS!

 

[MT Headed]

EK is famous for distinguishing between distance and displacement. Your v^2= v0^2 +2a(delta x) equation is great for answering displacement (i.e. xfinal - xinitial) questions.

I think the big takeaway is you need to be more paranoid about the key phrase "toal distance" vs. "displacement".

 

[justphuta]

Thanks for that catch!!