1
IIT-JEE 2012 Paper 1 Offline
MCQ (Single Correct Answer)
+3
-1

A small mass m is attached to a massless string whose other end is fixed at P as shown in the figure. The mass is undergoing circular motion in the xy-plane with centre at O and constant angular speed $$\omega$$. If the angular momentum of the system, calculated about O and P are denoted by $${\overrightarrow L _O}$$ and $${\overrightarrow L _P}$$, respectively, then

A
$${\overrightarrow L _O}$$ and $${\overrightarrow L _P}$$ do not vary with time.
B
$${\overrightarrow L _O}$$ varies with time while $${\overrightarrow L _P}$$ remains constant.
C
$${\overrightarrow L _O}$$ remains constant while $${\overrightarrow L _P}$$ varies with time.
D
$${\overrightarrow L _O}$$ and $${\overrightarrow L _P}$$ both vary with time.
2
IIT-JEE 2012 Paper 1 Offline
MCQ (Single Correct Answer)
+3
-1

A biconvex lens is formed with two planoconvex lenses as shown in the figure. Refractive index n of the first lens is 1.5 and that of the second lens is 1.2. Both curved surface are of the same radius of curvature R = 14 cm. For this biconvex lens, for an object distance of 40 cm, the image distance will be

A
$$-$$280.0 cm
B
40.0 cm
C
21.5 cm
D
13.3 cm
3
IIT-JEE 2012 Paper 1 Offline
MCQ (Single Correct Answer)
+3
-1

A thin uniform rod, pivoted at O, is rotating in the horizontal plane with constant angular speed $$\omega$$, as shown in the figure. At time t = 0, a small insect starts from O and moves with constant speed v, with respect to the rod towards the other end. It reaches the end of the rod at t = T and stops. The angular speed of the system remains $$\omega$$ throughout. The magnitude of the torque (|$$\tau$$|) about O, as a function of time is best represented by which plot ?

A
B
C
D
4
IIT-JEE 2012 Paper 1 Offline
MCQ (Single Correct Answer)
+3
-1

Three very large plates of same area are kept parallel and close to each other. They are considered as ideal black surfaces and have very high thermal conductively. The first and third plates are maintained at temperatures 2T and 3T, respectively. The temperature of the middle (i.e. second) plate under steady state condition is

A
$${\left( {{{65} \over 2}} \right)^{1/4}}T$$
B
$${\left( {{{97} \over 4}} \right)^{1/4}}T$$
C
$${\left( {{{97} \over 2}} \right)^{1/4}}T$$
D
$${(97)^{1/4}}T$$
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