Assertion: The slope of momentum versus time curve give us the acceleration.

Reason: Acceleration is given by the rate of change of momentum.

A system consists of three masses $m_1\text{,} m_2$ and $m_3$ connected by a string passing over a pulley $P$. The mass $m_3$ hangs freely and $m_2$ and $m_1$ are on a rough horizontal table (the coefficient of friction$=\mu$). The pulley is frictionless and of negligible mass. The downward acceleration of mass $m_1$ is (assume, $m_1=$$m_2=m_3=m$),

Three blocks with masses $m\text{,} 2m$ and $3m$ are connected by strings as shown in the figure. After an upward force $F$ is applied on block $m$, the masses move upward with constant speed $v$. What is the net force on the block of mass $2m$? $(g$ is the acceleration due to gravity)

Three blocks $A\text{,} B$ and $C$ of masses $4 \mathrm{kg}\text{,} 2 \mathrm{kg}$ and $1 \mathrm{kg}$, respectively, are in contact on a frictionless surface as shown. If a force of $14 \mathrm{N}$ is applied on the $4 \mathrm{kg}$ block, then the contact force between $A$ and $B$ is,