Tbr physics example chapter 1

[crazy person]

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For chapter 1, on page 20, when they said they arrived at the equation y= 1/2at by using equation v= vo+at, isn't this wrong? shouldn't it be from equation y= vot + 1/2 at^2?

on page 23, they also said, using equation 1.18 which is y=1/2at^2 ? when it should be v=vo +at, right? and the answer should be -4s not 4s, right?

I think there is an error they made or am I wrong?

 

[dudewheresmymd]

For chapter 1, on page 20, when they said they arrived at the equation y= 1/2at by using equation v= vo+at, isn't this wrong? shouldn't it be from equation y= vot + 1/2 at^2?



on page 23, they also said, using equation 1.18 which is y=1/2at^2 ? when it should be v=vo +at, right? and the answer should be -4s not 4s, right?



I think there is an error they made or am I wrong?

1) Correct. In 1.15, there is no yo so yes a typo.

2) Correct. Just a typo...you'll find a lot as you trek through TBR. No the answer is 4s, time can never be negative (it doesn't make any sense).

v=voy+at
0=40+-10t
-40/-10=4s

define up as positive so voy is positive and acceleration is negative

Also, please don't post multiple times regarding the same topic.

 

[crazy person]

Thanks !
and yes I know, I'm still new to this and figuring this whole thing out.