What is the difference between speed and velocity?

Speed is the rate of change of distance — it is a scalar quantity (only magnitude). Velocity is the rate of change of displacement — it is a vector quantity (has both magnitude and direction). Example: A car going at 60 km/h has a speed of 60 km/h, but its velocity is 60 km/h towards north (direction matters).

What are the three equations of motion?

The three equations of uniformly accelerated motion are: (1) v = u + at — relates final velocity to initial velocity, acceleration, and time; (2) s = ut + ½at² — relates displacement to initial velocity, acceleration, and time; (3) v² = u² + 2as — relates final velocity to initial velocity, acceleration, and displacement. Here u = initial velocity, v = final velocity, a = acceleration, t = time, s = displacement.

What does the slope of a velocity-time graph represent?

The slope of a velocity-time graph represents acceleration. If the slope is positive (graph rises), the object has positive acceleration (speeding up). If the slope is negative (graph falls), the object is decelerating (slowing down). If the slope is zero (horizontal line), the object moves at constant velocity with zero acceleration.

Velocity and Acceleration

Motion • Class 9 Science • NCERT • CBSE

Velocity is the rate of change of displacement (vector), while speed is the rate of change of distance (scalar). Acceleration is the rate of change of velocity. The three equations of motion — v = u + at, s = ut + ½at², v² = u² + 2as — are the most important formulas from this chapter.

Key Formulas

v = u + at
s = ut + ½at²
v² = u² + 2as
a = (v − u) / t

Frequently Asked Questions

What is the difference between speed and velocity?: Speed is the rate of change of distance — it is a scalar quantity (only magnitude). Velocity is the rate of change of displacement — it is a vector quantity (has both magnitude and direction). Example: A car going at 60 km/h has a speed of 60 km/h, but its velocity is 60 km/h towards north (direction matters).
What are the three equations of motion?: The three equations of uniformly accelerated motion are: (1) v = u + at — relates final velocity to initial velocity, acceleration, and time; (2) s = ut + ½at² — relates displacement to initial velocity, acceleration, and time; (3) v² = u² + 2as — relates final velocity to initial velocity, acceleration, and displacement. Here u = initial velocity, v = final velocity, a = acceleration, t = time, s = displacement.
What does the slope of a velocity-time graph represent?: The slope of a velocity-time graph represents acceleration. If the slope is positive (graph rises), the object has positive acceleration (speeding up). If the slope is negative (graph falls), the object is decelerating (slowing down). If the slope is zero (horizontal line), the object moves at constant velocity with zero acceleration.

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