A mass of $2\, kg$ suspended with thread $AB$ (figure). Thread $CD$ of the same type is attached to the other end of $2\, kg$ mass. if the lower thread is pulled with a jerk, what happens ?

Write condition for equilibrium when two force act on a particle.

Two masses $m$ and $M$ are attached to the strings as shown in the figure. If the system is in equilibrium, then 

A body of mass $60\,kg$ is suspended by means of three strings $P, Q$ and $R$ as shown in the figure is in equilibrium. The tension in the string $P$ is $..........g\,N$

A book is lying on the table. What is the angle between the action of the book on the table and the reaction of the table on the book?

A pebble of mass $0.05\; kg$ is thrown vertically upwards. Give the direction and magnitude of the net force on the pebble,

$(a)$ during its upward motion,

$(b)$ during its downward motion,

$(c)$ at the highest point where it is momentarily at rest.

Do your answers change if the pebble was thrown at an angle of $45^o$ with the horizontal direction? Ignore air resistance.