Formula Used
Initial kinetic energy: KEinitial = 1/2 m1u12 + 1/2 m2u22
Final kinetic energy: KEfinal = 1/2 m1v12 + 1/2 m2v22
Energy lost: Energy lost = KEinitial - KEfinal
Loss percent: Loss percent = Energy lost / KEinitial × 100
Restitution mode: e = relative speed after impact / relative speed before impact
The calculator uses SI values internally. It converts your selected units before solving.
How to Use This Calculator
- Select the calculation mode.
- Choose mass, velocity, and output energy units.
- Enter both masses and initial velocities.
- Enter final velocities if they are known.
- Enter restitution if final speeds must be estimated.
- Use negative velocity for the opposite direction.
- Press the calculate button.
- Review energy loss, momentum, and restitution checks.
- Download the CSV or PDF report when needed.
Example Data Table
| Object 1 Mass | Object 2 Mass | Initial v1 | Initial v2 | Final v1 | Final v2 | Initial KE | Final KE | Energy Lost |
|---|---|---|---|---|---|---|---|---|
| 2 kg | 3 kg | 5 m/s | 0 m/s | 0.5 m/s | 3 m/s | 25 J | 13.75 J | 11.25 J |
| 1 kg | 1 kg | 4 m/s | -2 m/s | -1 m/s | 3 m/s | 10 J | 5 J | 5 J |
| 5 kg | 2 kg | 2 m/s | 0 m/s | 1.2 m/s | 2 m/s | 10 J | 7.6 J | 2.4 J |
Understanding Collision Energy Loss
A collision changes motion because forces act during contact. Total momentum may stay constant in a closed system. Kinetic energy does not always stay constant. Some energy can become heat, sound, vibration, deformation, or internal energy. This calculator helps estimate that change with clear inputs and useful checks.
Why Energy Loss Matters
Energy loss shows how inelastic a crash or impact is. A small loss means the bodies bounce well. A large loss means the bodies stick, bend, or warm up. Physics students use this value in lab reports. Engineers use it when studying bumpers, balls, packaging, and machine stops.
What The Calculator Measures
The tool compares kinetic energy before impact with kinetic energy after impact. You can enter final velocities directly. You can also estimate them from a coefficient of restitution. That option uses momentum and rebound behavior together. It works best for straight line motion.
Interpreting The Result
A positive energy loss means kinetic energy decreased. Zero loss means an ideal elastic collision. A negative value means the final speeds contain more kinetic energy than the initial speeds. That can happen if stored energy, an engine, or a user input error is present. The momentum check helps find mistakes.
Better Input Practice
Use consistent signs for direction. Motion to the right can be positive. Motion to the left can be negative. Mass must be positive. The restitution value should usually be between zero and one. A value near zero suggests a sticky impact. A value near one suggests a strong bounce.
Practical Notes
Real impacts are complex. Rotation, friction, spin, and deformation can change results. The calculator uses a one dimensional model, so it is a clean estimate. For accurate experiments, measure velocities carefully. Repeat the trial several times. Average the values. Then compare the percentage loss across materials.
Common Uses
Use it for carts, balls, blocks, pendulums, and crash tests. It can support class demonstrations and quick design checks. The result also helps compare padding choices. Lower loss may mean better rebound. Higher loss may mean better impact absorption. Always match the model to the situation. If bodies rotate or slide, treat the answer as an estimate. Document every assumption before sharing results.
FAQs
What is energy lost in a collision?
It is the decrease in kinetic energy after impact. The missing kinetic energy usually becomes heat, sound, vibration, deformation, or internal energy.
Can momentum stay constant while energy is lost?
Yes. In a closed system, total momentum can stay constant. Kinetic energy can still decrease during an inelastic collision.
What does a negative energy loss mean?
It means final kinetic energy is greater than initial kinetic energy. Check the signs, units, and speeds. Stored energy may also be involved.
When should I use restitution mode?
Use restitution mode when final velocities are unknown. Enter the coefficient of restitution, and the calculator estimates final speeds from momentum and rebound behavior.
What unit is used inside the calculation?
The calculator converts values to kilograms, meters per second, and joules. Then it converts the final energy result to your selected unit.
Why are negative velocities allowed?
Velocity includes direction. A negative value can represent motion in the opposite direction. Use one sign convention throughout the problem.
Is zero energy loss possible?
Yes. Zero loss means an ideal elastic collision. Real collisions often lose some kinetic energy through sound, heat, and deformation.
Can this handle two-dimensional collisions?
No. This page uses a one-dimensional model. For two-dimensional impacts, split velocity into components and analyze each direction carefully.