In circular motion, why don’t centripetal and centrifugal forces cancel each other? Well, they don’t cancel each other because they are not present simultaneously for the same observer. Only one is present at a time for one observer. If you take ground observer – inertial observer to be more precise – then only centripetal force is applicable and of course it is applicable towards the centre. There is no centrifugal force present here. Since both are not present simultaneously, they don’t cancel each other. In case of non-inertial or accelerated observer, only centrifugal force is present – it acts away from the centre. There is no centripetal force applicable. Since both are not present simultaneously, they can’t cancel each other.
Category Archives: Physics
Distant planet having a radius of 3,000 km …
Consider a distant planet having a radius of 3,000 kilometres and unknown mass. If an object is dropped from a height of 1,500 kilometres, what will be its velocity just before it hits the ground? (Assume the acceleration due to gravity on planet’s surface is 3 m/s².)
(A) 3,000 m/s
(B) 1,000 m/s
(C) 2,000 m/s
(D) Mass of the planet is required
Speed of Sound in Dry Air
Which of the following is the closest formula to find the speed of sound in dry air? ( $\gamma=1.4$, M=28.97 gm/mole)
| (A) $v=\sqrt T. 20$ | (B) $v=\sqrt {T.20}$ |
| (C) $v=T.20$ | (D) $T20$ is related to Cricket only |
A heavy nucleus Q of half-life 20 minutes …
A heavy nucleus Q of half-life 20 minutes undergoes alpha-decay with probability of 60% and beta-decay with probability of 40%. Initially, the number of Q nuclei is 1000. The number of alpha-decays of Q in the first one hour is
(A) 50 (B) 75 (C) 350 (D) 525 Continue reading A heavy nucleus Q of half-life 20 minutes …
An $\alpha$-particle (mass 4 amu) and a singly ….
An $\alpha$-particle (mass 4 amu) and a singly charged sulfur ion (mass 32 amu) are initially at rest. They are accelerated through a potential V and then allowed to pass into a region of uniform magnetic field which is normal to the velocities of the particles. Within this region, the $\alpha$-particle and the sulfur ion move in circular orbits of radii $r_{\alpha}$ and $r_S$, respectively. The ratio ($r_S/r_\alpha$) is _____. Continue reading An $\alpha$-particle (mass 4 amu) and a singly ….
The first three spectral lines of H-atom ….
The first three spectral lines of H-atom in the Balmer series are given by $\lambda_1,\lambda_2,\lambda_3$ respectively. Considering the Bohr atomic model, the ratio of wave lengths of first and third spectral lines $\frac {\lambda_1}{\lambda_3}$ is approximately given by $’x’ \times 10^{-1}$.
The value of x, to the nearest integer is———–. Continue reading The first three spectral lines of H-atom ….
Frequency of potential energy in SHM = ?
A body is executing simple harmonic motion with frequency ‘n’, the frequency of its potential energy is:
(1) n (2) 2n
(3) 3n (4) 4n Continue reading Frequency of potential energy in SHM = ?