Q. A body weighs $6\, gms$ when placed in one pan and $24 \, gms$ when placed on the other pan of a false balance. If the beam is horizontal when both the pans are empty, the true weight of the body is :

Laws of Motion Report Error

A

$13 \, gm$

B

$12 \, gm$

C

$15.5\, gm$

D

$15 \, gm$

Solution:

Let length of beam is ' $l$ ', and the two pans are at a distance of ' $x$ ' and ' $l-x$ ' from the hinged point. If true weight of body is $A$, then
$A x =6(l-x) \,\,\,$...(1)
$A(1-x) =24 x\,\,\,$ ...(2)
2Dividing (1) by (2), we get
$\frac{6}{A} =\frac{A}{24} $
$A^{2} =144 $
$A =12 \,g m$

Questions from Laws of Motion

1. A car of mass 1000 kg moves on a circular track of radius 20 m. If the coefficient of friction is 0.64, then the maximum velocity with which the car moves is

JIPMER 2013

2. A stone of mass $1 \,kg$ is lying on the floor of a train which is accelerating with $1\, m \,s^{-2}$. The net force acting on the stone is

3. In the following figure, an object of mass $ 1.2\, kg $ is at rest at point $ P $ . lf $ R $ and $ F $ are the reaction and the frictional force, respectively, then

AMU 2011

4. A bomb moving with velocity $\left(40\hat{i}+50\hat{j}-25\hat{k}\right)m s^{-1}$ explodes into two pieces of mass ratio $1 : 4$. After explosion the smaller piece moves away with velocity $\left(200\hat{i}+70\hat{j}-15\hat{k}\right)m s^{-1}$. The velocity of larger piece after explosion is

AIIMS 2018

5. A coin placed on a rotating table just slips if it is placed at a distance $4r$ from the centre. If we double the angular velocity of the table, then the coin will just slip when it is away from the centre at a distance equal to

NTA Abhyas 2020

Physics Most Viewed Questions

1. If $E$ and $G$ respectively denote energy and gravitational constant, then $\frac{ E }{ G }$ has the dimensions of:

NEET 2021 Physical World, Units and Measurements

2. The de Broglie wavelength of an electron moving with kinetic energy of $144 \,eV$ is nearly

NEET 2020 Dual Nature of Radiation and Matter

3. A car starts from rest and accelerates at $5\, m / s ^{2}$ At $t=4\, s$, a ball is dropped out of a window by a person sitting in the car. What is the velocity and acceleration of the ball at $t =6\, s$ ? (Take $\left. g =10\, m / s ^{2}\right)$

NEET 2021 Motion in a Straight Line

4. A wheel with $20$ metallic spokes each $1\, m$ long is rotated with a speed of $120\, rpm$ in a plane perpendicular to a magnetic field of $0.4\, G$. The induced emf between the axle and rim of the wheel will be, $(1 G = 10^{-4}\, T)$

NEET 2020 Electromagnetic Induction

5. A barometer is constructed using a liquid (density $= 760 \,kg/m^{3})$ What would be the height of the liquid column, when a mercury barometer reads $76\, cm$ ?
(density of mercury $= 13600 kg/m^{3})$

NEET 2020 Mechanical Properties of Fluids