$A$ mass $M$ is suspended by a system of light inextensible strings as shown in the figure. Find the tension in the horizontal string.

Explain the main types of forces with suitable examples.

Ten one-rupee coins are placed on top of each other on a table. Each coin has a mass $m$. Give the magnitude and direction of:
$(a)$ The force on the $7^{\text{th}}$ coin (counted from the bottom) due to all the coins on its top.
$(b)$ The force on the $7^{\text{th}}$ coin by the $8^{\text{th}}$ coin.
$(c)$ The reaction of the $6^{\text{th}}$ coin on the $7^{\text{th}}$ coin.

Which of the following groups of forces could be in equilibrium?

$A$ mass $M \text{ kg}$ is suspended by a weightless string. The horizontal force required to hold the mass at $60^{\circ}$ with the vertical is

Two spherical objects each of radii $R$ and masses $m_1$ and $m_2$ are suspended using two strings of equal length $L$ as shown in the figure $(R << L)$. The angle $\theta$ which mass $m_2$ makes with the vertical is approximately