$A$ bird weighs $2 \ kg$ and is inside a closed cage of $1 \ kg$. If it starts flying,then what is the weight of the bird and cage assembly in $kg$?

$A$ man pulls a block heavier than himself with a light horizontal rope. The coefficient of friction is the same between the man and the ground,and between the block and the ground.

$A$ block is placed on a rough horizontal plane. $A$ time-dependent horizontal force $F = Kt$ acts on the block,where $K$ is a positive constant. The acceleration-time graph of the block is:

$A$ sphere of mass $m$ and radius $R$ is kept on a rough horizontal surface and pulled with a horizontal force $F = \alpha t$,where $\alpha$ is a constant and $t$ is time. The coefficient of static friction is $\mu_s$ and the coefficient of kinetic friction is $\mu_k$. Which of the following graphs correctly shows the variation of the acceleration of the sphere with time?

Two fixed frictionless inclined planes making an angle $30^\circ$ and $60^\circ$ with the vertical are shown in the figure. Two blocks $A$ and $B$ are placed on the two planes. What is the relative vertical acceleration of $A$ with respect to $B$?

On which factors does the stopping distance of a vehicle depend?