問9

(1)\(v\ =\ v_0+\ at\)

\(10\ =\ 50\ +\ a\times10\)

    \(10a\ =\ -40\)

\(∴a=\ -4.0\)m/s^2

 

(2)\(v^2-{v_0}^2\ =\ 2ax\)

\(x\ =\ \frac{v^2-{v_0}^2}{2a}\)

\(=\frac{{10}^2\ -\ {25}^2}{2\times(-4.0)}\)

\(=\ 300\)m