What is acceleration? What is the formula for it?

Acceleration is the rate at which an object's velocity changes over time—whether by speeding up, slowing down, or changing direction. It's a vector quantity, meaning it has both magnitude (how much change) and direction (which way the change occurs). The fundamental formula is a = Δv / Δt or a = (v - u) / t, measuring the change in velocity (Δv) divided by the time interval (Δt) over which that change occurs. Acceleration is measured in units of meters per second squared (m/s²), representing how many meters per second the velocity changes every second.

Understanding acceleration requires distinguishing it from velocity and position. While position tells you where an object is, and velocity tells you how fast it's moving, acceleration tells you how the motion itself is changing. A car cruising at constant 60 mph has zero acceleration (unchanging velocity), while a car speeding up from 60 to 70 mph in 10 seconds has positive acceleration of 1.47 m/s². Even an object moving at constant speed in a circle accelerates because its direction continuously changes—this centripetal acceleration keeps it in curved motion rather than straight-line travel.

Real-world acceleration governs everything from vehicle performance (0-60 mph times) to gravitational effects (9.8 m/s² downward) to human tolerance limits (fighter pilots experience 9g acceleration in tight turns, while normal elevator rides limit acceleration to 0.15g for comfort). Acceleration is what you feel when motion changes—the backward push when a car accelerates forward, the lightness when an elevator accelerates upward, the sideways force in a turning vehicle. This sensation arises because acceleration requires force (F = ma), and that force acts on your body, creating the physical experience of changing motion.