# Thread: speed of car

1. ## speed of car

wondering if anyone can help me ...i need answers for A and B...thanks

2. Originally Posted by carlasader
wondering if anyone can help me ...i need answers for A and B...thanks
For a)

$\displaystyle v = u + at$
$\displaystyle v = 10 + (3)(6)$
$\displaystyle v = 10 + 18$
$\displaystyle v = 28 \ m.s^{-1}$

For b)

From O to A

$\displaystyle v^2 = u^2 + 2as$
$\displaystyle 100 = 0 + 2(4)(s)$
$\displaystyle s = 12,5 \ metres$

From A to B

$\displaystyle s = ut + \frac{1}{2} at$
$\displaystyle s = (10)(6) + \frac{1}{2} (3)(6)$
$\displaystyle s = 60 + \frac{1}{2} (18)$
$\displaystyle s = 69$

Add those two answers together to get OB...
Thus OB = 12,5 + 69 = 71,5 metres

3. Originally Posted by janvdl
...
From A to B

$\displaystyle s = ut + \frac{1}{2} at$
$\displaystyle s = (10)(6) + \frac{1}{2} (3)(6)$
$\displaystyle s = 60 + \frac{1}{2} (18)$
$\displaystyle s = 69$

Add those two answers together to get OB...
Thus OB = 12,5 + 69 = 71,5 metres
Hello,

you have a small but very effective typo in your calculations:

From A to B

$\displaystyle s = ut + \frac{1}{2} at^2$
$\displaystyle s = (10)(6) + \frac{1}{2} (3)(36)$
$\displaystyle s = 60 + \frac{1}{2} (108)$
$\displaystyle s = 114$

Add those two answers together to get OB...
Thus OB = 12,5 + 114= 126.5 metres