i neeed to figure out the distance and the speed of the car so i need 4 and 5 that ,thank you ...thanks in advance for help !
Hello,
to #4:
You have 2 forces which can be described by vectors:
$\displaystyle \overrightarrow{f_1}=\left( \begin{array}{c}p \\ 10 \end{array} \right)$ and $\displaystyle \overrightarrow{f_2}=\left( \begin{array}{c}3 \\ 5 \end{array} \right)$
The resulting force can be described by: $\displaystyle \overrightarrow{f_r}=\left( \begin{array}{c}p+3 \\ 15 \end{array} \right)$
From $\displaystyle F = m \cdot a$ you know that $\displaystyle F =2 \frac{m}{s^2} \cdot 8.5 kg = 17 N = \left | \overrightarrow{f_r}\right|$
Thus you get:
$\displaystyle 17^2 = (3+p)^2+15^2\ \ \Longleftrightarrow \ \ p^2+6p-55=0$
You'll get the solutions: $\displaystyle p_1=5 \text{ or } p_2=-11$