Download App

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

Rajasthan BoardEnglish MediumSTD 11 SciencePhysics3.2 , motion in plane1 Mark
MCQ
A projectile is fired with a speed $u$ at an angle $\theta$ with the horizontal. Its speed when its direction of motion makes an angle ‘$\alpha $’ with the horizontal is
  • A
    $u\,\, sec\theta \,\,cos\alpha$
  • B
    $u\,\, sec\theta\,\, sin\alpha$
  • ✓
    $u \,\,cos\theta \,\,sec\alpha$
  • D
    $u\,\, sin \theta \,\,sec\alpha$
✓

Answer

Correct option: C.
$u \,\,cos\theta \,\,sec\alpha$
c
Horizontal component of velocity $=v_{x}=u \cos \theta$

 vertical component of velocity $v_{y}=u \sin \theta-g t$

angle of velocity with horizontal $=\alpha$

$\tan a=\frac{v_{y}}{v_{x}}=\frac{(u \sin \theta-g t)}{(4 \cos \theta)}$

$t=\frac{u(\sin \theta-\cos \theta \tan \alpha)}{g}$

$v_{y}=u \cos \theta \tan \alpha$

$v_{x}=u \cos \theta$

So the speed of the projectile $=\sqrt{\left(\left(v_{x}\right)^{2}+\left(v_{y}\right)^{2}\right)}$

 $=u \cos \theta \sec \alpha$

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 truck is moving on the horizontal road with constant speed $v.$  A ball is thrown from the truck vertical up at speed  $u$  $w.r.t.$  truck. What is distance traversed by the truck when ball returns on the truck
→
In the given figure for $u\ =\ u_0/3$ , find the height from the ground at which the block leaves the hemisphere [where $u_0\ =\ \sqrt {\frac{{gr}}{3}} ]$
→
One quarter sector is cut from a uniform circular disc of radius $R$.  This sector has mass $M$. It is made to rotate about a line perpendicular to its plane and passing through the centre of the original disc.  Its moment of inertia about the axis of rotation is
→
A thin rod of length $L$ is bent to form a semicircle. The mass of rod is $M$. What will be  the gravitational potential at the centre of the circle?
→
A sonometer wire resonates with a given tuning fork forming standing waves with five antinodes between the two bridges when a mass of $9\,kg$ is suspended from the wire. When this mass is replaced by a mass $M,$ the wire resonates with the same tuning fork forming three antinodes for the same positions of the bridges. The value of $M$ is .... $kg$
→
The sum of two forces acting at a point is $16\, N.$ If the resultant force is $8\, N$ and its direction is perpendicular to minimum force then the forces are
→
A rope of mass $5 \,kg$ is hanging between two supports as shown alongside. The tension at the lowest point of the rope is close to ........... $N$ (take, $g=10 \,m / s ^{2}$ )
→
In the experiment for the determination of the speed of sound in air using the resonance column method, the length of the air column that resonates in the fundamental mode, with a tuning fork is $0.1\,m$. when this length is changed to $0.35\,m,$ the same tuning fork resonates with the first overtone. Calculate the end correction  .... $m$
→
A tuning fork $A$ produces $4$ beats/sec with another tuning fork $B$ of frequency $320 Hz$. On filing the fork $A$, $4$ beats/sec are again heard. The frequency of fork $A$, after filing is ....$Hz$
→
A car is moving with a constant speed of $20\,m / s$ in a circular horizontal track of radius $40\,m$. A bob is suspended from the roof of the car by a massless string. The angle made by the string with the vertical will be : (Take $g =10$ $\left.m / s ^2\right)$
→