1
IIT-JEE 2008 Paper 2 Offline
+3
-1

Consider a system of three charges $${q \over 3},{q \over 3}$$ and $$- {{2q} \over 3}$$ placed at points A, B and C, respectively, as shown in the figure. Take O to be the centre of the circle of radius R and angle CAB = 60$$^\circ$$

A
The electric field at point O is $${q \over {8\pi {\varepsilon _0}{R^2}}}$$ directed along the negative x-axis
B
The potential energy of the system is zero
C
The magnitude of the force between the charges at C and B is $${{{q^2}} \over {54\pi {\varepsilon _0}{R^2}}}$$
D
The potential at point O is $${q \over {12\pi {\varepsilon _0}R}}$$
2
IIT-JEE 2008 Paper 2 Offline
+3
-1

A radioactive sample S1 having activity of 5 $$\mu$$Ci has twice the number of nuclei as another sample S2 which has an activity of 10 $$\mu$$Ci. The half lives of S1 and S2 can be :

A
20 years and 5 years, respectively
B
20 years and 10 years, respectively
C
10 years each
D
5 years each
3
IIT-JEE 2008 Paper 2 Offline
+3
-1

A transverse sinusoidal wave moves along a string in the positive x-direction at a speed of 10 cm/s. The wavelength of the waves is 0.5 m and its amplitude is 10 cm. At a particular time t, the snap-shot of the wave is shown in figure. The velocity of point P when its displacement is 5 cm is :

A
$${{\sqrt {3\pi } } \over {50}}\widehat j$$ m/s
B
$$- {{\sqrt {3\pi } } \over {50}}\widehat j$$ m/s
C
$${{\sqrt {3\pi } } \over {50}}\widehat i$$ m/s
D
$$- {{\sqrt {3\pi } } \over {50}}\widehat i$$ m/s
4
IIT-JEE 2008 Paper 2 Offline
+3
-1

A block (B) is attached to two unstretched springs S1 and S2 with spring constants k and 4k respectively (see figure I). The other ends are attached to identical supports M1 and M2 not attached to the walls. The springs and supports have negligible mass. There is no friction anywhere. The block displaced towards wall 1 by a small distance x (figure II) and released. The block returns and moves a maximum distance y towards wall 2. Displacements x and y are measured with respect to the equilibrium position of the block B. The ratio $$\frac{y}{x}$$ is :

A
4
B
2
C
$$\frac{1}{2}$$
D
$$\frac{1}{4}$$
EXAM MAP
Medical
NEET