Đáp án:
bài 1
$\begin{array}{l}
a.a = 0,167\left( {m/{s^2}} \right)\\
b.{F_{ms}} = 1000\left( N \right)\\
F = 1167\left( N \right)
\end{array}$
bài 2
$\begin{array}{l}
a.k = 500\left( {N/m} \right)\\
b.{l_2} = 56\left( {cm} \right)
\end{array}$
Giải thích các bước giải:
bài 1
$\begin{array}{l}
a.\left\{ \begin{array}{l}
t = 1p = 60s\\
v = 36km/h = 10m/s
\end{array} \right.\\
a = \frac{{\Delta v}}{t} = \frac{{10 - 0}}{{60}} = \frac{1}{6} = 0,167\left( {m/{s^2}} \right)\\
b.N = P = mg = 1000.10 = 10000\left( N \right)\\
{F_{ms}} = \mu N = 0,1.10000 = 1000\left( N \right)\\
F - {F_{ms}} = ma\\
\Rightarrow F = 1000 + 1000.0,167 = 1167\left( N \right)
\end{array}$
bài 2
$\begin{array}{l}
a.\Delta {l_1} = {l_1} - {l_0} = 54 - 50 = 4\left( {cm} \right) = 0,04\left( m \right)\\
k = \frac{{{m_1}g}}{{\Delta {l_1}}} = \frac{{2.10}}{{0,04}} = 500\left( {N/m} \right)\\
b.\Delta {l_2} = \frac{{\left( {{m_1} + {m_2}} \right)g}}{k} = \frac{{\left( {2 + 1} \right).10}}{{500}} = 0,06\left( m \right) = 6\left( {cm} \right)\\
{l_2} = {l_0} + \Delta {l_2} = 56\left( {cm} \right)
\end{array}$
