WBJEE · Physics · Center of Mass Momentum and Collision
Two particles \(A\) and \(B\) (both initially at rest) start moving towards each other under a mutual force of attraction. At the instant, when the speed of \(A\) is \(v\) and the speed of \(B\) is \(2 v\), the speed of the centre of mass is
- A zero
- B \(v\)
- C \(\frac{3 v}{2}\)
- D \(-\frac{3 v}{2}\)
Answer & Solution
Correct Answer
(A) zero
Step-by-step Solution
Detailed explanation
In the absence of external force the speed \[ u_{\mathrm{co}}=0 \] \(F_{ext}=0\) then \[ v_{\mathrm{cm} .}=0 \text { always } \]
See the Complete Solution
Get step-by-step explanations for this and 2.5 Lakh+ more JEE, NEET & CET questions.
- Unlock all solutions
- Practice the full chapter
- Track accuracy across PYQs
4.8 rated on Google Play · 14,000+ reviews
More questions from Physics
- In a region, the intensity of an electric field is given by \(\mathbf{E}=2 \mathbf{i}+3 \mathbf{j}+\mathbf{k}\) in \(\mathrm{NC}^{-1}\). The electric flux through a surface \(\mathbf{S}=10 \mathbf{i} \mathrm{m}^{2}\) in the region isWBJEE 2012 Easy
- A uniform rod of length \(L\) pivoted at one end \(P\) is freely rotated in a horizontal plane with an angular velocity \(\omega\) about a vertical axis passing through \(\mathrm{P}\). If the temperature of the system is increased by \(\Delta \mathrm{T}\), angular velocity becomes \(\frac{\omega}{2}\). If coefficient of linear expansion of the rod is \(\alpha(\alpha< < 1)\), then \(\Delta \mathrm{T}\) will beWBJEE 2021 Easy
- Two pith balls, each carrying charge \(+q\) are hung from a hook by two strings. It is found that when each charge is tripled, angle between the strings double. What was the initial angle between the strings?WBJEE 2020 Hard
- A train is moving along the tracks at a constant speed \(\mathrm{u}\). A girl on the train throws a ball of mass \(m\) straight ahead along the direction of motion of the train with speed \(v\) with respect to herself. ThenWBJEE 2023 Medium
- If \(\chi\) stands for the magnetic susceptibility of a substance, \(\mu\) for its magnetic permeability and \(\mu_{0}\) for the permeability of free space, thenWBJEE 2017 Easy
-
As shown in the figure, a pump is designed as horizontal cylinder with a piston having area A and an outlet orifice having an area ' \(a\) '. The piston moves with a constant velocity under the action of force \(F\). If the density of the liquid is \(\rho\), then the speed of the liquid emerging from the orifice is, (assume \(A > > a\) )WBJEE 2023 Hard
More PYQs from WBJEE
- When \(100 \mathrm{~g}\) of boiling water at \(100^{\circ} \mathrm{C}\) is added into a calorimeter containing \(300 \mathrm{~g}\) of cold water at \(10^{\circ} \mathrm{C}\), temperature of the mixture becomes \(20^{\circ} \mathrm{C}\). Then a metallic block of mass \(1 \mathrm{~kg}\) at \(10^{\circ} \mathrm{C}\) is dipped into the mixture in the calorimeter. After reaching thermal equilibrium, the final temperature becomes \(19^{\circ} \mathrm{C}\). What is the specific heat of the metal in C.G.S. unit?WBJEE 2020 Medium
- ln a\(\Delta A B C,\) if \(\angle C=90^{\circ}, r\) and \(R\) are the inradius and circumrodius of the ABC respectively, then \(2(r+R)\) is equal toWBJEE 2015 Hard
- The wavelength of second Balmer line in hydrogen &spectrum is 600 nm The wavelength for its third line in Lyman series isWBJEE 2016 Medium
- The point in the interval \([0,2 \pi]\), where \(f(x)=e^x \sin x\) has maximum slope, isWBJEE 2010 Medium
- In hemoglobin the metal ion present isWBJEE 2010 Easy
- If aniline is treated with conc. \(\mathrm{H}_{2} \mathrm{SO}_{4}\) and heated at \(200^{\circ} \mathrm{C}\), the product isWBJEE 2018 Easy