Velocity Calculator – v = d/t
Calculate velocity, distance, or time using v = d/t.
How It Works
Enter any two of distance, time, or velocity. The calculator solves for the third variable using the kinematics equation v = d/t. Distance is in meters, time in seconds, and velocity in m/s. Use the "Solve for" selector to choose which variable you want to find.
Formula
Step-by-Step Examples
Example 1: Finding Velocity
A sprinter runs 100 meters in 9.58 seconds (Usain Bolt's world record). What is his average velocity?
- v = d / t = 100 / 9.58 = 10.44 m/s (about 37.6 km/h)
Example 2: Finding Distance
A car travels at 30 m/s (108 km/h) for 2.5 hours. What distance does it cover?
- Convert time: 2.5 hours = 9,000 seconds
- d = v × t = 30 × 9,000 = 270,000 m = 270 km
Example 3: Finding Time
Light travels at 3×10⁸ m/s. How long does it take to travel from the Moon to Earth (384,400 km)?
- Convert distance: 384,400 km = 3.844×10⁸ m
- t = d / v = 3.844×10⁸ / 3×10⁸ = 1.28 seconds
Speed and Velocity Unit Conversion Reference
Real-World Applications
- Transportation: Speed cameras use v = d/t over a fixed road distance to calculate a vehicle's average speed.
- Athletics: Race timing systems calculate average velocity for every leg of a sprint or swim race.
- Astronomy: Spacecraft velocity is calculated from distance and travel time using this same formula.
- Physics experiments: Students measure the time a ball takes to roll a known distance to determine its velocity.
Frequently Asked Questions
What is the difference between speed and velocity?
Speed is a scalar quantity — it only has magnitude (e.g., 60 km/h). Velocity is a vector — it has both magnitude and direction (e.g., 60 km/h north). The formula v = d/t gives average speed when distance is the total path length. It gives average velocity only when the object travels in a straight line without reversing direction.
How do I convert m/s to km/h?
Multiply m/s by 3.6. For example, 10 m/s × 3.6 = 36 km/h. To convert back, divide km/h by 3.6. The factor 3.6 comes from the ratio of seconds to hours (3600) divided by meters to kilometers (1000): 3600/1000 = 3.6.
What is average velocity vs. instantaneous velocity?
Average velocity is total displacement divided by total time — what this calculator computes. Instantaneous velocity is the velocity at one specific moment in time, which requires calculus (the derivative of position with respect to time). For objects moving at constant speed, average and instantaneous velocity are the same.
Can velocity be negative?
Yes. Negative velocity means the object is moving in the opposite direction to the positive reference direction. For example, if rightward is positive, a ball moving leftward at 5 m/s has a velocity of −5 m/s. The speed (magnitude) is still 5 m/s.