# Work, Energy and Power (KVPY Stream SB-SX (Class 12 & 1st Year B.Sc.) Physics): Questions 4 - 5 of 21

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## Question number: 4

» Work, Energy and Power » Work Done

Appeared in Year: 2012

MCQ▾

### Question

A conducting rod of mass m and length l is free to move without friction on two parallel long conducting rails, as shown below. There is a resistance R across the rails. In the entire space around, there is a uniform magnetic field B normal to the plane of the rod and rails. The rod is given an impulsive velocity v0.

Finally, the initial energy

### Choices

Choice (4) Response

a.

will be converted fully into magnetic energy due to induced current

b.

will enable rod to continue to move with velocity v0 since the rails are frictionless

c.

will be converted fully into heat energy in the resistor

d.

will be converted into the work done against the magnetic field

## Question number: 5

» Work, Energy and Power » Elastic and Inelastic Collisions

Appeared in Year: 2011

MCQ▾

### Question

An electron collides with free molecules initially in its ground state. The collision leaves the molecules in an excited state that is metastable and does not decay to the ground state by radiation. Let K be the sum of the initial kinetic energies of the electron and the molecule, and P the sum of their initial momenta. Let K’ and P’ represent the same physical quantities after the collision. Then –

### Choices

Choice (4) Response

a.

b.

c.

d.

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