A train is moving at a constant speed V. When its driver observes… - Vidyadip

MCQ

A train is moving at a constant speed $V$. When its driver observes another train in front of him on the same track and moving in the same direction with constant speed $u$. If the distance between the trains be $x$, then what should be the minimum retardation of the train so as to avoid collision?

A
$(V + u)^2\,/x$
B
$(V -u)^2\,/x$
C
$(V + u)^2\,/2x$
✓
$(V -u)^2\,/2x$

✓

Answer

Correct option: D.

$(V -u)^2\,/2x$

d
Here relative velocity of the train $w.r.t.$ other

$\operatorname{train}=V-u$

Hence,

$0-(\mathrm{V}-\mathrm{u})^{2}=2 \mathrm{ax}$ or $\mathrm{a}=-\frac{(\mathrm{V}-\mathrm{u})^{2}}{2 \mathrm{x}}$

Minimum retardation $=\frac{(\mathrm{V}-\mathrm{u})^{2}}{2 \mathrm{x}}$

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free

Explore more

JEE STD 11 Science question papers→Gujarat Board STD 11 Science question papers→Gujarat Board question paper generator→

Similar questions

In a charged capacitor, the energy resides

A $200\, W$ sodium street lamp emits yellow light of wavelength $0.6\, \mu m$. Assuming it to be $25\%$ efficient in converting electrical energy to light, the number of photon of yellow light it emits per second is

A presbyopic patient has near point as $30\, cm$ and far point as $40\, cm$. The dioptric power for the corrective lens for seeing distant objects is:-

A uniform rod of mass $m$ and length $l$ is moving with velocity $u$ in a direction perpendicular to its length. A blow of impulse $J$ is given perpendicular to its length at a distance $\frac{l}{4}$ from its centre at point $P$ such that instantaneous velocity of point $P$ is $2u$. Then the velocity of its centre of mass will be.

$Assertion :$ A body that is good radiator is also a good absorber of radiation at a given wavelength.
$Reason :$ According to Kirchhoff’s law the absorptivity of a body is equal to its emissivity at a given wavelength.

If a watch with a wound spring is taken on to the moon, it

In a $p-n$ junction diode the direction of diffusion current is from

Let $R _1$ be the radius of the second stationary orbit and $R_2$ be the radius of the fourth stationary orbit of an electron in Bohr's model. The ratio $\frac{ R _1}{ R _2}$ is

A body takes $10\, minutes$ to cool from $60\,^oC$ to $50\,^oC$. The temperature of surroundings is constant at $25\,^oC$. Then, the temperature of the body after next $10\, minutes$ will be approximately ....... $^oC$

A uniformly charged solid sphere of radius $R$ has potential $V_0$ (measured with respect to $\infty$) on its surface. For this sphere the equipotential surfaces with potentials $\frac{{3{V_0}}}{2},\;\frac{{5{V_0}}}{4},\;\frac{{3{V_0}}}{4}$ and $\frac{{{V_0}}}{4}$ have rasius $R_1,R_2,R_3$ and $R_4$ respectively. Then