$A$ car travels from point $A$ to point $B$ with a speed of $40 \ km/h$ and returns from $B$ to $A$ with a speed of $60 \ km/h$. What is the average speed of the car for the entire journey (in $km/h$)?

$A$ mass of $2.9 \ kg$ is suspended from a string of length $50 \ cm$ and is at rest. Another body of mass $100 \ g$,which is moving horizontally with a velocity of $150 \ m/s$,strikes and sticks to it. Subsequently,when the string makes an angle of $60^{\circ}$ with the vertical,the tension in the string is $(g=10 \ m/s^2)$. (in $N$)

$\int_0^{\pi / 2} \frac{d x}{1+\tan ^3 x}$ is equal to :

An object is attached to the bottom of a light vertical spring and set vibrating. The maximum speed of the object is $15 \, cm/s$ and the period is $628 \, ms$. The amplitude of the motion in centimeters is

$\int \frac{1+\cos 4 x}{\cot x-\tan x} d x$ is equal to

If $5x - 12y + 10 = 0$ and $12y - 5x + 16 = 0$ are two tangents to a circle,then the radius of the circle is