Two nuclei collide,one originally at rest,in an endothermic nuclear reaction with Q = −2.05 MeV.Which of the following describes the minimum kinetic energy needed in the reactant nuclei for the reaction is to occur?
A)equal to 2.05 MeV
B)greater than 2.05 MeV
C)less than 2.05 MeV
D)exactly half of 2.05 MeV

Question

Quizplus · Accepted Answer

In an endothermic reaction, energy needs to be supplied to the system for the reaction to occur. The minimum energy required is the Q-value of the reaction, which in this case is -2.05 MeV (note the negative sign indicates an endothermic reaction). 
By conservation of energy, the initial kinetic energy of the two nuclei must equal the Q-value of the reaction for the reaction to occur. Since one nucleus is initially at rest, the other nucleus must have a kinetic energy of at least 2.05 MeV in order to meet the minimum energy requirement. Therefore, the correct choice is B: greater than 2.05 MeV.

Two Nuclei Collide,one Originally at Rest,in an Endothermic Nuclear Reaction