9.4 × 10⁻¹⁹ J. (2 sig. fig).
The kinetic energy of an object depends on its mass and its speed. Mass is given for this neutron. However, the speed of the neutron needs to be found.
What's the speed of this neutron?
[tex]\text{Speed} = \dfrac{\text{Distance Traveled}}{\text{Time Taken}} = \dfrac{12\;\text{m}}{3.6\times10^{-4}\;\text{s}} = 3.33\times 10^{4}\;\text{m}\cdot\text{s}^{-1}[/tex]
(3 sig. fig. Speed is an intermediate quantity. Include at least one more sig. fig. for the value of kinetic energy to be accurate to 2 sig. fig.)
What's the kinetic energy of this neutron?
[tex]\text{Kinetic Energy} = \dfrac{1}{2}\cdot m\cdot v^{2}[/tex],
where
[tex]\text{Kinetic Energy} = \dfrac{1}{2}\cdot m\cdot v^{2}\\\phantom{\text{Kinetic Energy}} = \dfrac{1}{2} \cdot 1.7\times 10^{-27} \;\text{kg} \times (3.33\times 10^{4} \;\text{m}\cdot\text{s}^{-1})^{2}\\\phantom{\text{Kinetic Energy}} =9.4\times 10^{-19}\;\text{kg}\cdot \text{m}^{2}\cdot\text{s}^{-2}\\\phantom{\text{Kinetic Energy}} =9.4\times 10^{-19}\;\text{J}[/tex].
(2 sig. fig as in mass, distance travelled, and time).
