Question

A 5-Kg block is placed on top of a 10-kg block (shown below). A horizontal force of 45 N is 

applied to the 10-kg block, and the 5-kg block is tied to the wall. The coefficient of kinetic 

friction between all moving surfaces is 0.2. (a) Draw a free body diagram for each block and 

identify the action-reaction forces between the blocks. (b) Determine the tension in the 

string and the magnitude of the acceleration of the 10-kg block.

Answer 1

a)

b)

$T=\mu m_1g=0.2\cdot5\cdot9.8=9.81\ N$

$45-\mu(m_1+m_2)g-\mu m_1g=m_2a$

$a=\frac{45-\mu(m_1+m_2)g-\mu m_1g}{m_2}=\frac{45-0.2(5+10)\cdot9.8-0.2\cdot5\cdot9.8}{10}=0.576\ m/s^2$