Physics
Velocity in Kinematics
Quick fact
A car traveling at 60 km/h in a circle has constant speed but constantly changing velocity because its direction changes.
Why this is interesting
You know how fast a car is going by looking at its speedometer, but why does it matter whether it's heading north or south?
Read the full explanation
Understanding Velocity in Kinematics
Imagine you're watching a runner on a straight track. You can time them and see how fast they go—that's their speed. But what if they run in a loop? Speed still tells you how fast, but you also need to know where they're heading to know if they're getting closer to the finish line. Velocity is the concept that combines both speed and direction. In physics, we define velocity as the change in position (called displacement) divided by the time taken. Displacement is the straight-line distance from start to end, including direction. So if you run 100 meters north in 10 seconds, your velocity is 10 m/s north. Speed would just be 10 m/s. Velocity tells you more because it gives the full picture of motion.
A deeper explanation
Velocity matters because it is a vector, which means it has both magnitude and direction. This is crucial for predicting where an object will be in the future. For instance, if you know the velocity of a projectile, you can compute its trajectory. Velocity also underpins the concept of acceleration: acceleration is the rate of change of velocity. So if you want to understand how forces affect motion (Newton's laws), you first need velocity. In kinematics, velocity is the bridge between position and acceleration. Without direction, you can't tell if an object is turning or just speeding up in a straight line. This is why velocity is a cornerstone of describing motion in physics.