Page 624 - SUBSEC October 2017_Neat

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Item 27 refers to the following diagram. Item 29 refers to the following dia-
gram.

27. A microwave transmitter X sends radio
waves to a metal sheet Y. A probe, P,
between X and Y is moved from one node
through 20 antinodes to a node 0.3 m away. 29. A mass, m, is attached to a vertical helical
What is the frequency of the microwaves spring and displaced a distance "A" from
emitted from X? equilibrium as shown in the diagram. The
mass is released so that it oscillates with
(A) 3 x 10 Hz simple harmonic motion with angular
-2
(B) 3 x 10 Hz frequency ω.
-8
(C) 2 x 10 Hz
10
(D) 1 x 10 Hz Which of the following expressions gives
10
the variation of velocity, v, with time, t?
(A) v = A sin ωt
28. Which of the following quantites does NOT (B)
remain constant when a particle moves in v = A cos ωt
simple harmonic motion? (C) v = A ω sin ωt
(D) v = -A ω sin ωt
2
(A) Force
(B) Amplitude
(C) Total energy Item 30 refers to the following dia-
(D) Angular frequency gram.

30. A mass m, undergoes horizontal simple
harmonic motion under the action of two
springs as shown. Its equation of motion
is and its amplitude is A.

What is its MAXIMUM kinetic
energy?

(A) ½ kA /m
2
(B) 2 m A /K
2
2
(C) 2 k A /m
2
2
(D) kA 2

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