Velocity Calculator – Calculate Speed with Direction
Calculate velocity from displacement and time. Unlike speed, velocity includes direction – making it a vector quantity essential for physics and engineering calculations.
Speed tells you how fast. Velocity tells you how fast AND which direction. Speed is a scalar (magnitude only). Velocity is a vector (magnitude + direction). This distinction matters in physics because direction affects outcomes.
Example: Round Trip
You drive 100 km north in 1 hour, then 100 km south in 1 hour. Your average speed is 100 km/h (200 km ÷ 2 h). But your average velocity is 0 km/h – you ended up where you started, so net displacement is zero.
Negative velocity doesn't mean "slower" – it means moving in the opposite direction. If positive is east, -50 m/s means 50 m/s west. The speed is still 50 m/s in both cases.
| Unit | Equals 1 m/s | Common Use |
|---|---|---|
| m/s | 1 m/s | SI unit, physics |
| km/h | 3.6 km/h | Road speeds (most countries) |
| mph | 2.24 mph | Road speeds (US, UK) |
| knots | 1.94 knots | Aviation, maritime |
| ft/s | 3.28 ft/s | Engineering (US) |
| Mach | ~0.0029 Mach | Aircraft speeds |
Mach 1 = speed of sound ≈ 343 m/s at sea level. Varies with temperature and altitude.
| Object/Phenomenon | Velocity | Context |
|---|---|---|
| Walking human | 1.4 m/s (5 km/h) | Casual walking pace |
| Sprinting human | 10 m/s (36 km/h) | Usain Bolt's top speed |
| Highway car | 28 m/s (100 km/h) | Typical highway speed |
| Commercial jet | 250 m/s (900 km/h) | Cruising speed |
| Speed of sound | 343 m/s (1235 km/h) | At sea level, 20°C |
| Earth orbiting Sun | 29,780 m/s | Average orbital velocity |
| Light (vacuum) | 299,792,458 m/s | Universal speed limit |
Can velocity be negative?
Yes. Negative velocity means moving in the opposite direction from your defined positive axis. If you define east as positive, a car going west at 50 km/h has velocity -50 km/h. The speed (magnitude) is still 50 km/h.
What's the difference between average and instantaneous velocity?
Average velocity = total displacement ÷ total time. Instantaneous velocity = velocity at a specific moment. Your car's speedometer shows instantaneous speed. If you drive 100 km in 2 hours, your average velocity is 50 km/h, even though you varied speed throughout.
How is acceleration related to velocity?
Acceleration is the rate of change of velocity. a = Δv / Δt. Positive acceleration means velocity is increasing. Negative acceleration (deceleration) means velocity is decreasing. An object can have zero velocity but non-zero acceleration (like a ball at the top of its trajectory).
Why use displacement instead of distance?
Displacement is the straight-line change in position (a vector). Distance is the total path length traveled (a scalar). Velocity uses displacement because it describes how position changes. A race car completing a lap has traveled distance but zero displacement – and therefore zero average velocity.
What is terminal velocity?
Terminal velocity is the constant speed a falling object reaches when air resistance equals gravitational force. For a skydiver in belly-down position, it's about 55 m/s (200 km/h). In a head-first dive, it can reach 90 m/s. With a parachute, it drops to about 5-7 m/s.
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