A truck is pulling a car out of a ditch by means of a steel cable that is $9.1\,m$ long and has a radius of $5\,mm$, when the car just begins to move the tension in the cable is $800\,N$. How much has the cable stretched ? (Young’s modulus for steel is $ 2 \times 10^{11}\,Nm^{-2}$)
$\mathrm{Y}=\frac{\mathrm{F} l}{\mathrm{~A} \Delta l}$
$\Delta l =\frac{\mathrm{F} l}{\mathrm{AY}}=\frac{\mathrm{F} l}{\pi r^{2} \mathrm{Y}}$
$\Delta l =\frac{800 \times 9.1}{3.14 \times\left(5 \times 10^{-3}\right)^{2} \times 2 \times 10^{11}}$
$=46.369 \times 10^{-5}$ $\approx 4.64 \times 10^{-4} \mathrm{~m}$
A weight of $200 \,kg$ is suspended by vertical wire of length $600.5\, cm$. The area of cross-section of wire is $1\,m{m^2}$. When the load is removed, the wire contracts by $0.5 \,cm$. The Young's modulus of the material of wire will be
A force of ${10^3}$ newton stretches the length of a hanging wire by $1$ millimetre. The force required to stretch a wire of same material and length but having four times the diameter by $1$ millimetre is
check the statment are True or False $:$
$(a)$ Young’s modulus of rigid body is .....
$(b)$ A wire increases by $10^{-6}$ times its original length when a stress of
$10^8\,Nm^{-2}$ is applied to it, calculate its Young’s modulus.
$(c)$ The value of Poisson’s ratio for steel is ......
A steel rod has a radius of $20\,mm$ and a length of $2.0\,m$. A force of $62.8\,kN$ stretches it along its length. Young's modulus of steel is $2.0 \times 10^{11}\,N / m ^2$. The longitudinal strain produced in the wire is $..........\times 10^{-5}$
A stone is tied to an elastic string of negligible mass and spring constant $k$. The unstretched length of the string is $L$ and has negligible mass. The other end of the string is fixed to a nail at a point $P$. Initially the stone is at the same level as the point $P$. The stone is dropped vertically from point $P$.
$(a)$ Find the distance $'y'$ from the top when the mass comes to rest for an instant, for the first time.
$(b)$ What is the maximum velocity attained by the stone in this drop ?
$(c)$ What shall be the nature of the motion after the stone has reached its lowest point ?