Q. 18

# A particle is in linear simple harmonic motion between two points A and B, 10 cm apart (Fig. 14.6). Take the direction from A to B as the + ve direction and choose the correct statements.

A. The sign of velocity, acceleration and force on the particle when it is 3 cm away from A going towards B are positive.

B. The sign of velocity of the particle at C going towards O is negative.

C. The sign of velocity, acceleration and force on the particle when it is 4 cm away from B going towards A are negative.

D. The sign of acceleration and force on the particle when it is at point B is negative.

Answer :

The force always acts in the direction of the mean position and at point C it is acting towards O and away from A. Thus positive.

Also, acceleration is in the direction of force thus it is also acting in the same direction as force and is positive.

Also, the direction of motion is towards A and thus velocity is also positive.

Hence option (a) is correct.

b) when particle is at C the velocity is in direction towards O thus positive and hence option (b) is incorrect.

c) when the particle is at 4 cm away from B and moving towards The acceleration and force are directed towards mean position O and also since it is moving towards A then all velocity, acceleration and force are negative in signs. Option c) is correct.

d) acceleration and force is always towards mean position O and thus at B the acceleration and force is negative. Thus correct.

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