NEET Physics: Waves – NCERT Masterclass & 100 MCQ Quiz

MOTION IN A STRAIGHT LINE

Detailed Notes & 5-Part Mega Quiz for NEET

1. Position, Path Length and Displacement

Motion is a change in position of an object with time. In kinematics, we describe motion without looking at its causes.

• Path Length (Distance): The total length of the actual path traversed by an object. It is a scalar quantity and always positive.
• Displacement: The shortest straight-line distance between the initial and final positions. It is a vector quantity and can be positive, negative, or zero.

2. Average Velocity and Average Speed

Average Velocity is the ratio of displacement to the time interval $(\Delta x / \Delta t)$. Average Speed is the total path length divided by the total time interval.

NEET Trick: Average speed is always greater than or equal to the magnitude of average velocity. They are equal only when the object moves in a straight line without reversing its direction.

3. Instantaneous Velocity and Acceleration

Instantaneous Velocity ($v$): The limit of average velocity as the time interval becomes infinitesimally small. It is the slope of the tangent on an $x-t$ graph.

$$v = \frac{dx}{dt} \quad|\quad a = \frac{dv}{dt}$$

Acceleration ($a$): The rate of change of velocity. The area under a $v-t$ curve represents the displacement of the object over a given time interval.

4. Kinematic Equations for Uniform Acceleration

For one-dimensional motion with a constant acceleration '$a$', we use the three kinematic equations:

• $v = v_0 + at$
• $x = v_0t + \frac{1}{2}at^2$
• $v^2 = v_0^2 + 2ax$

5. Motion Under Free Fall

An object released near the surface of the Earth is accelerated downward by gravity ($g \approx 9.8 \text{ m/s}^2$).

Galileo's Law of Odd Numbers: The distances traversed by a body falling from rest in equal intervals of time stand to one another in the same ratio as the odd numbers: 1 : 3 : 5 : 7...

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🚀 NEET MEGA QUIZ (100 QUESTIONS)

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