$A$ 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 $kg$?

$A$ helicopter of mass $1000 \;kg$ rises with a vertical acceleration of $15\; m s^{-2}$. The crew and the passengers weigh $300\; kg$. Give the magnitude and direction of the
$(a)$ force on the floor by the crew and passengers,
$(b)$ action of the rotor of the helicopter on the surrounding air,
$(c)$ force on the helicopter due to the surrounding air.

In the figure,two blocks are connected by a uniform strut attached to each block with frictionless pins. Block $A$ weighs $400 \, N$,block $B$ weighs $300 \, N$,and the strut $AB$ weighs $200 \, N$. If $\mu = 0.25$ under block $B$,determine the minimum coefficient of friction under block $A$ to prevent motion.

$A$ cylinder is placed on a rough plank,which in turn is placed on a smooth surface. The plank is pulled with a constant force $F$. Indicate the correct direction of the friction force acting on the cylinder.

$A$ metallic block of mass $20 \ kg$ is dragged with a uniform velocity of $0.5 \ ms^{-1}$ on a horizontal table for $2.1 \ s$. The coefficient of kinetic friction between the block and the table is $0.10$. What will be the maximum possible rise in temperature of the metal block if the specific heat of the block is $0.1 \ cal \ g^{-1} \ ^{\circ}C^{-1}$ (in $^{\circ} C$)? Assume $g = 10 \ ms^{-2}$ and a uniform rise in temperature throughout the whole block. [Ignore absorption of heat by the table]

$A$ solid ball is suspended from the ceiling of a motor car through a light string. $A$ transverse pulse travels at the speed $60 \text{ cm/s}$ on the string, when the car is at rest. When the car accelerates on a horizontal road, the speed of the pulse is $66 \text{ cm/s}$. The acceleration of the car is nearly $\left(g=10 \text{ m/s}^2\right)$ (in $\text{ m/s}^2$)