\[Q=(m_i-m_f)c^2\]
Variables
Qreaction energy released or absorbed (J)
mi[m_i]initial total rest mass (kg)
mf[m_f]final total rest mass (kg)
cspeed of light in vacuum (m/s)
Description
What is this formula?
This formula calculates the Q-value of a nuclear reaction from the difference between the initial and final rest masses. A positive Q-value means the reaction releases energy, while a negative Q-value means energy must be supplied.
When to use it
Use this formula to analyze nuclear reactions, particle reactions, fission, fusion, decay processes, and nuclear energy balance problems.
Example
Given:
mi=3.3500×10^-27 kg
mf=3.3460×10^-27 kg
c=2.9979×10^8 m/s
Formula:
Q=(mi-mf)c²
Substitution:
Q=(3.3500×10^-27-3.3460×10^-27)(2.9979×10^8)²
Result:
Q=3.59×10^-13 J
Applications
- Nuclear reaction analysis
- Fusion and fission calculations
- Particle physics
- Nuclear decay energy
- Reactor energy balance