Kinematic Equations Solver
Solve SUVAT kinematic motion equations for displacement, velocity, acceleration, and time.
Updated
What is the Kinematic Equations Solver?
Use the SUVAT equations to solve for one unknown in a linear-motion problem with constant acceleration. Enter compatible values for:
- Displacement (s)
- Initial Velocity (u)
- Final Velocity (v)
- Acceleration (a)
- Time (t)
The solver supports selected combinations of known values and reports an error when it cannot solve the combination you enter. It assumes consistent units and does not convert them.
How it works
1. Input Known Values
Enter the values you know for displacement (s), initial velocity (u), final velocity (v), acceleration (a), and time (t). Use consistent units (for example, metres, seconds, m/s, and m/s²); the tool does not convert units.
2. Mark the Unknown
Click the "Unknown" button next to the variable you want to solve for. Only one variable can be unknown at a time.
3. Get Results
The tool automatically selects and applies the correct SUVAT equation based on your inputs. Results are displayed instantly with your chosen precision.
4. Copy or Clear
Use the Copy button to copy individual or all results to your clipboard. The "Clear All" button resets the tool for new calculations.
Supported Equations
The solver uses the following SUVAT equations for constant acceleration:
| Equation | Description |
|---|---|
| s = ut + ½at² | Displacement with initial velocity and acceleration |
| v = u + at | Final velocity with initial velocity and acceleration |
| v² = u² + 2as | Final velocity squared with displacement and acceleration |
| s = ½(u + v)t | Displacement with average velocity |
| s = vt - ½at² | Displacement with final velocity and acceleration |
The solver supports the listed relationships and selected combinations of known variables; some combinations cannot be solved by this tool.
Precision Control
Adjust the displayed decimal places using the Precision dropdown. Changing display precision does not change the underlying calculation or determine significant figures.
Error Handling
The solver validates all inputs and provides clear error messages for:
- Invalid or non-numeric inputs
- Physically impossible scenarios (e.g., negative discriminant)
- Division by zero
- Missing or extra unknown variables
Examples
Find final velocity
Calculate final velocity when initial velocity, acceleration, and time are known.
u = 5 m/s, a = 2 m/s², t = 3 s, v = ?v = 11 m/sFind displacement
Calculate displacement when initial velocity, final velocity, and time are known.
u = 10 m/s, v = 20 m/s, t = 5 s, s = ?s = 75 mFind time
Calculate time when displacement, initial velocity, and acceleration are known.
s = 100 m, u = 0 m/s, a = 5 m/s², t = ?t ≈ 6.3246 sFind acceleration
Calculate acceleration when initial velocity, final velocity, and time are known.
u = 0 m/s, v = 30 m/s, t = 6 s, a = ?a = 5 m/s²Find initial velocity
Calculate initial velocity when displacement, acceleration, and time are known.
s = 50 m, a = 3 m/s², t = 4 s, u = ?u ≈ 4.5826 m/sFrequently asked questions
What are the SUVAT kinematic equations?
What are the SUVAT kinematic equations?
The SUVAT equations relate s (displacement), u (initial velocity), v (final velocity), a (acceleration), and t (time) for linear motion with constant acceleration.
What units should I use?
What units should I use?
You can use any consistent set of units, but the most common are:
- Displacement (s): meters (m)
- Velocity (u, v): meters per second (m/s)
- Acceleration (a): meters per second squared (m/s²)
- Time (t): seconds (s) The solver does not convert units, so ensure all your inputs use a compatible system.
Why do I get "No real solution" or "No positive time solution" errors?
Why do I get "No real solution" or "No positive time solution" errors?
These errors can occur when a selected equation has no real solution for the inputs or the solver finds no non-negative time. They can indicate incompatible values or a combination the solver does not support. Check the values, signs, units, and assumptions.
- An object accelerating in the opposite direction of its motion but still increasing speed.
- A displacement that cannot be achieved with the given acceleration and time.
- A final velocity that is less than the initial velocity with positive acceleration. Double-check your inputs for consistency.
Can I solve for more than one unknown at a time?
Can I solve for more than one unknown at a time?
Mark one variable as unknown and enter the other four. The solver then uses a supported equation combination; it does not guarantee a solution for every set of values.
Why is my result negative?
Why is my result negative?
Negative values can be physically meaningful in kinematics:
- Negative displacement (s): The object is moving in the opposite direction of your defined coordinate system.
- Negative velocity (u, v): The object is moving in the opposite direction of your coordinate system.
- Negative acceleration (a): Acceleration points in the negative direction of your coordinate system; whether the object speeds up or slows down depends on its velocity. The solver looks for a non-negative time solution. A negative-time mathematical result may describe motion before the chosen reference time rather than a future elapsed time.
How accurate are the calculations?
How accurate are the calculations?
The solver uses floating-point arithmetic. The Precision control changes how many decimal places are displayed; it does not guarantee physical accuracy or replace appropriate significant figures.
Can I use this for projectile motion?
Can I use this for projectile motion?
Yes, but with some considerations:
- Vertical motion: Use a = 9.81 m/s² (gravity) or a = -9.81 m/s² (if your coordinate system defines upward as positive).
- Horizontal motion (no air resistance): Use a = 0.
- 2D projectile motion: Solve the horizontal (x) and vertical (y) components separately, as they are independent of each other.
What if my acceleration is zero?
What if my acceleration is zero?
If acceleration (a = 0), the equations reduce to constant-velocity motion. For example:
- v = u (final velocity equals initial velocity)
- s = ut (displacement equals initial velocity multiplied by time)
- t = s/u (time equals displacement divided by initial velocity, if u ≠ 0) The solver handles some zero-acceleration cases when the selected inputs are supported.
Can I use this tool for circular motion or rotational kinematics?
Can I use this tool for circular motion or rotational kinematics?
No. This solver is designed for linear motion with constant acceleration (SUVAT equations). For circular or rotational motion, you would need to use angular kinematic equations, which involve angular displacement, angular velocity, angular acceleration, and torque. These are not supported by this tool.
How do I interpret the results for real-world scenarios?
How do I interpret the results for real-world scenarios?
Always consider the context of your problem:
- Sign: Positive/negative values indicate direction relative to your coordinate system.
- Magnitude: Ensure the values are realistic for your scenario (e.g., a car’s acceleration of 100 m/s² is unrealistic).
- Units: Double-check that your inputs and outputs use consistent units.
Related tools
More utilities you might find handy.
Density Calculator
Calculate density, mass, or volume instantly with full unit conversion and material comparison
Frequency to Wavelength Converter
Convert wave frequency and wavelength using a selected or custom propagation speed.
Molar Mass Calculator
Estimate a compound's molar mass from its formula, including supported nested groups and hydrate notation.