IIT-JEE 2011 · Paper 2 · Physics Q28

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PhysicsSingle correct+3 / -1Question 28 of 60

A wooden block performs SHM on a frictionless surface with frequency, $\nu_0$ . The block carries a charge $+Q$ on its surface. If now a uniform electric field $\vec E$ is switched-on as shown, then the SHM of the block will be

Block carrying +Q on a horizontal frictionless floor, attached by a spring to a wall on the right; the field E points to the right.

of the same frequency and with shifted mean position.

of the same frequency and with the same mean position.

of changed frequency and with shifted mean position.

of changed frequency and with the same mean position.

Answer and worked solution

Official answer: A

New equilibrium. The constant force $QE$ shifts the mean position by $\dfrac{QE}k$ (spring compressed).

Frequency. The restoring force about the new mean is still $-kx$ , so $\nu=\dfrac1{2\pi}\sqrt{\dfrac km}=\nu_0$ is unchanged.

(A)

Topics:Spring-mass systems Electric field

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IIT-JEE 2011 · Paper 2, Physics question 28