JEE Mains · Physics · STD 11 - Newtons laws of motion
- JEE Mains 2021
- Hard
- MCQ
The boxes of masses \(2\, {kg}\) and \(8\, {kg}\) are connected by a massless string passing over smooth pulleys. Calculate the time taken by box of mass \(8\; {kg}\) to strike the ground starting from rest. (use \(\left.{g}=10\, {m} / {s}^{2}\right)\) (in \({s}\))

Pick an option to check your answer.
Answer & Solution
Correct Answer
(D) \(0.4\)
Step-by-step Solution
Detailed explanation
\(\left({m}_{1} {g}-2 {T}\right)={m}_{1} {a}.....(1)\)
\({T}-{m}_{2} {g}={m}_{2}(2 {a})\)
\(2 {T}-2 {m}_{2} {g}=4 {m}_{2} {a}.....(2)\)
\({m}_{1} {g}-2 {m}_{2} {g}=\left({m}_{1}+4 {m}_{2}\right) {a}\)
\({S}=\frac{1}{2} {at}^{2}\)
\(\frac{0.2 \times 2 \times 4}{10}={t}^{2}\)
\({t}=0.4\, {sec}\)
More questions from Physics
- \(2\, kg\) of a monoatomic gas is at a pressure of \(4\times10^4\, N/m^2\). The density of the gas is \(8\, kg/m^3\). What is the order of energy of the gas due to its thermal motion ?JEE Mains 2019 Medium
- Find the magnetic field at point \(P\) due to a straight line segment \(AB\) of length \(6\, cm\) carrying a current of \(5\, A\). (See figure) \((\mu _0 = 4p\times10^{-7}\, N-A^{-2})\)
JEE Mains 2019 Hard - The critical angle for a denser-rarer interface is \(45^{\circ}\). The speed of light in rarer medium is \(3 \times 10^8\) ms. The speed of light in the denser medium is:JEE Mains 2023 Medium
- The position vectors of two 1 kg particles, (A) and (B), are given by
\(\overrightarrow{\mathrm{r}}_{\mathrm{A}}=\left(\alpha_1 \mathrm{t}^2 \hat{i}+\alpha_2 \mathrm{t} \hat{j}+\alpha_3 \mathrm{t} \hat{k}\right) \mathrm{m}\) and \(\overrightarrow{\mathrm{r}}_{\mathrm{B}}=(\beta_1 \mathrm{t} \hat{i}+\beta_2 \mathrm{t}^2 \hat{j}\) \(+\beta_3 \mathrm{t} \hat{k}) \mathrm{m}\), respectively; \((\alpha_1=1 \mathrm{~m} / \mathrm{s}^2, \alpha_2=3 \mathrm{n} \mathrm{m} / \mathrm{s},\) \(\alpha_3=2 \mathrm{~m} / \mathrm{s},\) \(\beta_1=2 \mathrm{~m} / \mathrm{s}, \beta_2=-1 \mathrm{~m} / \mathrm{s}^2, \beta_3=4 \mathrm{pm} / \mathrm{s})\), where t is time, n and p are constants. At \(t=1 \mathrm{~s},\left|\overrightarrow{V_A}\right|=\left|\vec{V}_B\right|\) and velocities \(\vec{V}_A\) and \(\vec{V}_B\) of the particles are orthogonal to each other. At \(t=1 \mathrm{~s}\), the magnitude of angular momentum of particle (A) with respect to the position of particle (B) is \(\sqrt{\mathrm{L}} \mathrm{kgm}^2 \mathrm{~s}^{-1}\). The value of L is _______ .JEE Mains 2025 Hard - Given below are two statements: Statement \(I\): An \(AC\) circuit undergoes electrical resonance if it contains either a capacitor or an inductor. Statement \(II\): An \(AC\) circuit containing a pure capacitor or a pure inductor consumes high power due to its non-zero power factor. In the light of above statements, choose the correct answer from the options given belowJEE Mains 2023 Medium
- Light emerges out of a convex lens when a source of light kept at its focus. The shape of wavefront of the light is _______.JEE Mains 2024 Hard
More PYQs from JEE Mains
- Match List - \(I\) with List - \(II\).
Choose the correct answer from the options given below :List - \(I\) \((Number)\) List - \(II\) \((Significant figure)\) \((A)\) \(1001\) \((I)\) \(3\) \((B)\) \(010.1\) \((II)\) \(4\) \((C)\) \(100.100\) \((III)\) \(5\) \((D)\) \(0.0010010\) \((IV)\) \(6\) JEE Mains 2024 Hard - A force \(\overrightarrow{ F }=4 \hat{ i }+3 \hat{ j }+4 \hat{ k }\) is applied on an intersection point of \(x =2\) plane and \(x\) -axis. The magnitude of torque of this force about a point \((2,3,4)\) is.......... . (Round off to the Nearest Integer)JEE Mains 2021 Hard
- As per the given figure, two plates \(A\) and \(B\) of thermal conductivity \(K\) and \(2 K\) are joined together to form a compound plate. The thickness of plates are \(4.0 \,cm\) and \(2.5 \,cm\) respectively and the area of cross-section is \(120 \,cm ^{2}\) for each plate. The equivalent thermal conductivity of the compound plate is \(\left(1+\frac{5}{\alpha}\right) K\), then the value of \(\alpha\) will be_______
JEE Mains 2022 Hard - For the four sets of three measured physical quantities as given below. Which of the following options is correct ? \((i)\) \(\mathrm{A}_{1}=24.36, \mathrm{B}_{1}=0.0724, \mathrm{C}_{1}=256.2\) \((ii)\) \(\mathrm{A}_{2}=24.44, \mathrm{B}_{2}=16.082, \mathrm{C}_{2}=240.2\) \((iii)\) \(\mathrm{A}_{3}=25.2, \mathrm{B}_{3}=19.2812, \mathrm{C}_{3}=236.183\) \((iv)\) \(\mathrm{A}_{4}=25, \mathrm{B}_{4}=236.191, \mathrm{C}_{4}=19.5\)JEE Mains 2020 Hard