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A proton and an electron, initially at rest, are allowed to move under their mutal attractive force. Their centre of mass will:

We require an external force to move the centre of mass of a system of particles. The mutual force of electrical attraction is an internal force... View Article

Two balls are thrown simultaneously in air. The acceleration of the centre of mass of the two balls, while in air

The only force acting on the balls is the force of gravity, so the acceleration of the centre of mass is equal to g. Since there is no force in... View Article

A shell following a parabolic path explodes somewhere in its flight. The centre of mass of fragments will continue to move in (a) Vertical direction (b) Same parabolic path (c) Horizontal direction (d) Any direction.

Option (b) - Same parabolic path The internal forces do not affect the trajectory of the centre of mass, and the forces due to explosion are the... View Article

Which of the following is not a binary system?

A binary system is one in which two bodies revolve about a common centre of mass. In earth-moon-sun system, center of mass lies in the sun. So,... View Article

Which of the following is the unit of angular acceleration?

The unit of angular acceleration is rad / s 2.... View Article

Which of the following statements give the relationship between linear velocity and angular velocity correctly?

Angular velocity (ω) = Linear velocity (v)/ radius (r).... View Article

A coil is wound as a transformer of rectangular cross-section. If all the linear dimensions of the transformer are increased by a factor 2 and the number of turns per unit length of the coil remain the same, the self inductance increased by a factor of

Self inductance L= μ0 N2 A / l = μ0 n2 lA Where n is the number of turns per unit length and N... View Article

A man standing on a table rotating about the central axis pulls his hands holding the dumb bells towards chest. How the angular velocity will change?

When the man pulls his hands towards chest, the moment of inertia will decrease and due to conservation of angular momentum, angular velocity... View Article

The centre of mass of the sun, earth, and moon system lies

The mass of the sun is very large as compared to that of earth and moon, therefore the centre of mass (CM) lies within the sun.... View Article

The external force for the earth moon system is due to

The gravitational attraction between earth and moon is the internal force to earth moon system, whereas attraction of the sun on both earth and... View Article

A stone of mass m tied to a string of length l is rotating along a circular path with constant speed v. The torque on the stone is

Because the angular acceleration is zero and hence the torque is zero.... View Article

A wheel with ten metallic spokes each 0.50 m long is rotated with a speed of 120 rev/min in a plane normal to the earth’s magnetic field at the place. If the magnitude of the field is 0.4 Gauss, the induced e.m.f. between the axle and the rim of the wheel is equal to

e = Bl2 πv = 0.4 X 10-4 X (0.5)2 X (3.14) X 120 / 60 = 6.28 X 10-5 V... View Article

A negative ion is an atom that ________ electrons

a negative ion is an atom that has gained one or more electrons.... View Article

Four billiards balls, each of mass 0.5 kg, all are travelling in the same direction on a billiard table, with speeds of 2 m/s, 4 m/s, 8 m/s and 10 m/s. What is the linear momentum of this system?

The linear momentum of a system is simply the sum of the linear momentum of the constituent parts. Thus we only need to find the momentum of... View Article

As a dancer performs a pirouette on her toes and draws her hands closer and starts spinning faster. This can be explained using

Conservation of angular momentum explains this. When she folds her arms and draws her hands closer her moment of inertia decreases and so as to... View Article

Put a pipe over the end of a wrench when trying to turn a stubborn nut on a bolt, to effectively make the wrench handle twice as long, you will increase the torque by

Torque = rotational force = force X lever arm If we make the lever arm twice as great, we increase the torque by two.... View Article

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