# Class 11 Physics Motion in a straight Line: NCERT Solutions for Question 20

This page focuses on the detailed Motion in a straight Line question answers for Class 11 Physics Motion in a straight Line, addressing the question: 'Figure 3.23 gives the x-t plot of a particle executing one-dimensional simple harmonic motion. (You will learn about this motion in more detail in Chapter14). Give the signs of position, velocity and acceleration variables of the particle at t = 0.3 s, 1.2 s, – 1.2 s.                                        (Fig 3.23)'. The solution provides a thorough breakdown of the question, highlighting key concepts and approaches to arrive at the correct answer. This easy-to-understand explanation will help students develop better problem-solving skills, reinforcing their understanding of the chapter and aiding in exam preparation.
Question 20

## Figure 3.23 gives the x-t plot of a particle executing one-dimensional simple harmonic motion. (You will learn about this motion in more detail in Chapter14). Give the signs of position, velocity and acceleration variables of the particle at t = 0.3 s, 1.2 s, – 1.2 s.                                       (Fig 3.23)

Negative, Negative, Positive (at t = 0.3 s)

Positive, Positive, Negative (at t = 1.2 s)

Negative, Positive, Positive (at t = –1.2 s)

For simple harmonic motion (SHM) of a particle, acceleration (a) is given by the relation:

a = – ω2x ω → angular frequency …………..… (i)

t = 0.3 s

In this time interval, x is negative. Thus, the slope of the x-t plot will also be negative.

Therefore, both position and velocity are negative.

However, using equation (i), acceleration of the particle will be positive.

t = 1.2 s

In this time interval, x is positive.

Thus, the slope of the x-t plot will also be positive.

Therefore, both position and velocity are positive.

However, using equation (i), acceleration of the particle comes to be negative.

t = – 1.2 s

In this time interval, x is negative. Thus, the slope of the x-t plot will also be negative. Since both x and t are negative, the velocity comes to be positive. From equation (i), it can be inferred that the acceleration of the particle will be positive.