# PHYSICS---am i doing anything wrong?

• Oct 7th 2009, 01:29 PM
Chokfull
PHYSICS---am i doing anything wrong?
Starting speed is 30 m/s
End speed is 15 m/s
Time elapsed is 3 s
Find the distance traveled (acceleration is constant)

the formula they gave me is

\$\displaystyle x-x^0=1/2(v^0+v)t\$

just pretend the \$\displaystyle ^0\$ is below not above, i dont know how to do sub-0 sorry.

anyway, i plug it all in and get

\$\displaystyle
1/2*(15+30)*3=67.5 m
\$

But the book says the answer is 90 m(Headbang)

thanks to any1 who helps! i think the book may be wrong, it wouldn't be the first time, but I'd like to be sure.
• Oct 7th 2009, 01:56 PM
Matt Westwood
Quote:

Originally Posted by Chokfull
Starting speed is 30 m/s
End speed is 15 m/s
Time elapsed is 3 s
Find the distance traveled (acceleration is constant)

the formula they gave me is

\$\displaystyle x-x^0=1/2(v^0+v)t\$

just pretend the \$\displaystyle ^0\$ is below not above, i dont know how to do sub-0 sorry.

anyway, i plug it all in and get

\$\displaystyle
1/2*(15+30)*3=67.5 m
\$

But the book says the answer is 90 m(Headbang)

thanks to any1 who helps! i think the book may be wrong, it wouldn't be the first time, but I'd like to be sure.

"am I doing anything wrong?" - yes, taking physics! (Smirk)

But seriously, if the time were 4 seconds, then yes the answer would be 90m. I reckon the book's wrong, because you're told it's 3 seconds.