For given systen ${\theta _1}$ ....... $^o$ 

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?

As shown in figure, a $70\,kg$ garden roller is pushed with a force of $\overrightarrow{ F }=200\,N$ at an angle of $30^{\circ}$ with horizontal. The normal reaction on the roller is $.......\,N$ $\left(\right.$ Given $\left.g =10\,m s ^{-2}\right)$

The restoring force of a spring with a block attached to the free end of the spring is represented by

A false balance has equal arms. An object weigh $X$ when placed in one pan and $Y$ when placed in other pan, then the weight $W$ of the object is equal to

A chain lying on an absolutely smooth table, half of it hanging over the edge of the table as shown in figure $(a)$. The time it takes to slip off the table is affected if two equal weights be attached, one to each end as shown in figure $(b)$ .
$t_a$ : time taken to slip in situation $'a'$
$t_b$ : time taken to slip in situation $'b'$