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← IIT-JEE 2011 · Paper 1
PhysicsSingle correct+3 / -1Question 37 of 69

IIT-JEE 2011 · Paper 1, Physics question 37

Passage

Paragraph for Question Nos. 35 to 37

Phase space diagrams are useful tools in analyzing all kinds of dynamical problems. They are especially useful in studying the changes in motion as initial position and momentum are changed. Here we consider some simple dynamical systems in one-dimension. For such systems, phase space is a plane in which position is plotted along horizontal axis and momentum is plotted along vertical axis. The phase space diagram is x(t) vs. p(t) curve in this plane. The arrow on the curve indicates the time flow. For example, the phase space diagram for a particle moving with constant velocity is a straight line as shown in the figure. We use the sign convention in which position or momentum upwards (or to right) is positive and downwards (or to left) is negative.

Momentum against position: a horizontal line at a positive momentum with an arrow pointing to the right (constant velocity).

Consider the spring-mass system, with the mass submerged in water, as shown in the figure. The phase space diagram for one cycle of this system is

A block hanging from a spring attached to a support, fully submerged in a tank of water.
Choose one option
Answer and worked solution

Official answer: B

Damped oscillation. In phase space SHM runs clockwise (positive momentum moves x to the right). Water damps the motion, so the amplitude decreases: a clockwise spiral that shrinks.

(B)