Download App

3.2 , motion in plane — Physics STD 11 Science — Question

Rajasthan BoardEnglish MediumSTD 11 SciencePhysics3.2 , motion in plane1 Mark
MCQ
Two particles start simultaneously from the same point and move along two straight lines, one with uniform velocity $v$ and other with a uniform acceleration $a$. If $\alpha$ is the angle between the lines of motion of two particles, then the least value of relative velocity will be at time given by
  • A
    $\frac{v}{a} \sin \alpha$
  • ✓
    $\frac{v}{a} \cos \alpha$
  • C
    $\frac{v}{a} \tan \alpha$
  • D
    $\frac{v}{a} \cot \alpha$
✓

Answer

Correct option: B.
$\frac{v}{a} \cos \alpha$
b
(b)

$v_r$ is subtraction of vector. Hence,

$v_r^2=x($ say $)=v^2+(a t)^2-2 v(a t) \cos \alpha$

Now, $v_r$ will be minimum when $x$ is minimum. Hence,

$\frac{d x}{d t}=0$ or $2 a^2 t-2 v a \cos \alpha=0$

$\therefore \quad t=\frac{v \cos \alpha}{a}$

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

More "M.C.Q (1 Marks)" from 3.2 , motion in plane→3.2 , motion in plane — all question types→Physics STD 11 Science question papers→Rajasthan Board STD 11 Science question papers→Rajasthan Board question paper generator→

Similar questions

A body is pulled along a rough horizontal surface with a velocity $6\,m/s$. If the body comes to rest after travelling $9\,m$ , then coefficient of sliding friction, is- (Take $g = 10\,m/s^2$ )
→
A student determined Young's Modulus of elasticity using the formula $Y=\frac{M g L^{3}}{4 b d^{3} \delta} .$ The value of $g$ is taken to be $9.8 \,{m} / {s}^{2}$, without any significant error, his observation are as following.

Physical Quantity Least count of the Equipment used for measurement Observed value
Mass $({M})$ $1\; {g}$ $2\; {kg}$
Length of bar $(L)$ $1\; {mm}$ $1 \;{m}$
Breadth of bar $(b)$ $0.1\; {mm}$ $4\; {cm}$
Thickness of bar $(d)$ $0.01\; {mm}$ $0.4 \;{cm}$
Depression $(\delta)$ $0.01\; {mm}$ $5 \;{mm}$

Then the fractional error in the measurement of ${Y}$ is

→
An object is projected at an angle of $45^°$ with the horizontal. The horizontal range and the maximum height reached will be in the ratio.
→
The gravitational potential energy of a body of mass $‘m’$ at the earth’s surface $ - mg{R_e}$. Its gravitational potential energy at a height ${R_e}$ from the earth’s surface will be (Here ${R_e}$ is the radius of the earth)
→
Of the following quantities, which one has dimensions different from the remaining three
→
Acceleration-time graph is given. If initial velocity is $5\,\,m/s,$  then velocity after $2$ $seconds$ is.......$m/s$
→
A spring balance is attached to the ceiling of a lift. $A$ man hangs his bag on the spring  and the spring reads $49 \,N$, when the lift is stationary. If the lift moves downward with  an acceleration of $5\, m/s^2$, the reading of the spring balance will be .......... $N$
→
The temperature of water at the surface of a deep lake is 2°C. The temperature expected at the bottom is:
  1. 0°C
  2. 2°C
  3. 4°C
  4. 6°C
→
The moment of inertia $I$ of a solid sphere having fixed volume depends upon its volume $V$ as
→
$Assertion$ : The driver in a vehicle moving with a constant speed on a straight road is in a noninertial frame of reference.
$Reason$ : A reference frame in which Newton's laws of motion are applicable is non-inertial.
→