WBJEE · Physics · Electrostatics
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?
- A \(30^{\circ}\)
- B \(60^{\circ}\)
- C \(45^{\circ}\)
- D \(90^{\circ}\)
Answer & Solution
Correct Answer
(B) \(60^{\circ}\)
Step-by-step Solution
Detailed explanation
Hint: \(\mathrm{T} \sin \theta=\mathrm{Fe}, \mathrm{T} \cos \theta=\mathrm{mg}\) \(\tan \theta=\frac{\mathrm{Fe}}{\mathrm{mg}}=\frac{\mathrm{k} \cdot \mathrm{q}^{2}}{(2 \mathrm{~L} \sin \theta)^{2} \mathrm{mg}}\) In 2 nd case…
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
- A small spherical body of radius \(r\) and density p moves with the terminal velocity \(v\) in a fluid of coefficient of viscosity \(\eta\) and density \(\bar{\sigma}\). What will be the net force on the body?WBJEE 2019 Easy
- Four charges equal to \(-Q\) are placed at the four corners of a square and a charge \(q\) is at its centre. If the system is in equilibrium, the value of \(q\) isWBJEE 2011 Medium
- Three infinite plane sheets carrying uniform charge densities \(-\sigma, 2 \sigma, 4 \sigma\) are placed parallel to \(X Z\) plane at \(Y=a, 3 a\), 4a respectively. The electric field at the point \((0,2 a, 0)\) isWBJEE 2021 Easy
- A metal plate of area \(10^{-2} \mathrm{~m}^2\) rests on a lauer of castor oil, \(2 \times 10^{-3} \mathrm{~m}\) thick whose coefficient of viscosity is \(1.55 ~Ns~ m^{-2}\). The approximate horizontal force required to move the plate with a uniform speed of \(3 \times 10^{-2} \mathrm{~ms}^{-1}\) isWBJEE 2024 Medium
- A horizontal semi-circular wire of radius \(\mathrm{r}\) is connected to a battery through two similar springs \(\mathrm{X}\) and \(\mathrm{Y}\) to an electric cell, which sends current I through it. A vertically downward uniform magnetic field B is applied on the wire, as shown in the figure. What is the force acting on each spring?
WBJEE 2022 Medium - Sound waves are passing through two routes-one in atraight path and the other along a semicireular path of radius \(r\) and are again combined into one pipe and superposed as shown in the figure. If the velocity of sound waves in the pipe is \(v\), then frequencies of resultant waves of maximum amplitude will be integral multiples of
WBJEE 2014 Easy
More PYQs from WBJEE
- Hybridisation of central atom in \(\mathrm{NF}_3\) isWBJEE 2009 Easy
- The angles of a triangle are in the ratio 2: 3: 7 and the radius of the circumscribed ircle is \(10 \mathrm{cm}\). The length of the smallest ide isWBJEE 2019 Medium
- If \(\vec{\alpha}\) is a unit vector, \(\vec{\beta}=\hat{\mathrm{i}}+\hat{\mathrm{j}}-\hat{\mathrm{k}}, \vec{\gamma}=\hat{\mathrm{i}}+\hat{\mathrm{k}}\), then the maximum value of \([\vec{\alpha} \vec{\beta} \vec{\gamma}]\) isWBJEE 2022 Easy
- Let \(u+v+w=3, u, v, w \in \mathbb{R}\) and \(f(x)=u x^2+v x+w\) be such that \(f(x+y)=f(x)+f(y)+x y, \forall x, y \in \mathbb{R}\). Then \(f(1)\) is equal toWBJEE 2025 Medium
- A capacitor of capacitance \(C\) is connected in series with a resistance \(R\) and \(D C\) source of emf \(E\) through a key. The capacitor starts charging when the key is closed. By the time the capacitor has been fully charged. what amount of energy is dissipated in the resistance \(R ?\)
WBJEE 2019 Easy - Which of the following would give a linear plot?
(\(k\) is the rate constant of an elementary reaction and \(\mathrm{T}\) is temp. in absolute scale)WBJEE 2023 Medium