Motion in Physics
Basic concepts of speed, velocity, and acceleration
1. Speed
Definition
Speed is defined as the distance traveled divided by the time of travel.
s = d / t
where s = speed, d = distance, t = time
Interactive Demo:
Use the controls below to experiment with different speeds and observe how distance changes with time.
2. Velocity
Vector vs Scalar
While speed is a scalar (only magnitude), velocity is a vector (magnitude + direction).
v = d / t (with direction)
Example: 50 mi/hr North, 25 m/s East
3. Acceleration
Rate of Change
Acceleration is the change in speed divided by the time it takes to make the change.
a = (vf - vā) / t
where vf = final speed, vā = initial speed, t = time
Interactive Demo:
Experiment with different acceleration values and observe how velocity changes over time.
š Key Equations Summary
Speed
s = d / t
Distance divided by time
Velocity
v = d / t
Speed with direction
Acceleration
a = Īv / t
Change in velocity over time
Important Note
Average speed doesn't tell us about motion at any particular instant. Only when moving with constant speed does average speed equal actual speed.