Two trains $A$ and $B$ initially $120\, km$ apart, start moving towards each other on the same track with a velocity of $60\, km/hr$ each. At the moment of start $A$ blows a whistle, which reflects on $B$ and subsequently reflects from $A$ and so on. Take the velocity of sound waves in air $1200\, km/hr$. The distance travelled by sound waves before the trains crash will be (in $km$)
$2400$
$1200$
$240$
$120$
A wave travelling along the $x- $ axis is described by the equation $y(x, t) = 0.005\,\,cos(\alpha x\,-\,\beta t).$ If the wavelength and the time period of the wave are $0.08 \,\,m$ and $2.0\,\,s,$ respectively, then $\alpha $ and $\beta $ in appropriate units are
A transverse wave is travelling along a stretched string from right to left. The figure shown represents the shape of the string at a given instant. At this instant
Two pipes are each $50\,cm$ in length. One of them is closed at one end while the other is both ends. The speed of sound in air is $340\,ms^{-1}.$ The frequency at which both the pipes can resonate is
A string of mass $2.5\, kg$ under some tension. The length of the stretched string is $20\, m$. If the transverse jerk produced at one end of the string takes $0.5\, s$ to reach the other end, tension in the string is .... $N$
A small source of sound moves on a circle as shown in the figure and an observer is standing on $O.$ Let $n_1,\, n_2$ and $n_3$ be the frequencies heard when the source is at $A, B$ and $C$ respectively. Then