![\lambda=\frac{c}{\nu}=\ \textgreater \ \nu=\frac{c}{\lambda}\\ ](https://tex.z-dn.net/?f=%5Clambda%3D%5Cfrac%7Bc%7D%7B%5Cnu%7D%3D%5C+%5Ctextgreater+%5C+%5Cnu%3D%5Cfrac%7Bc%7D%7B%5Clambda%7D%5C%5C%0A)
Воспользуемся формулой Эйнштейна для фотоэффекта:
![h\nu=A_{out}+\frac{mv^2}{2}\\ \frac{hc}{\lambda}=\frac{hc}{\lambda_{max}}+\frac{mv^2}{2}\\ \frac{mv^2}{2}=hc(\frac{1}{\lambda}-\frac{1}{\lambda_{max}})\\ v=\sqrt{\frac{2hc}{m}(\frac{1}{\lambda}-\frac{1}{\lambda_{max}})}\\ v=\sqrt{\frac{2*6.63*10^{-34}*3*10^8}{9.1*10^{-31}}(\frac{1}{380*10^{-9}}-\frac{1}{580*10^{-9}})}=\\=\sqrt{4.4*10^{5}*10^{9}(\frac{1}{380}-\frac{1}{580})}=\sqrt{4.4*10^{14}*9*10^{-4}}=6.3*10^5 m/s\\630km/s](https://tex.z-dn.net/?f=h%5Cnu%3DA_%7Bout%7D%2B%5Cfrac%7Bmv%5E2%7D%7B2%7D%5C%5C%0A%5Cfrac%7Bhc%7D%7B%5Clambda%7D%3D%5Cfrac%7Bhc%7D%7B%5Clambda_%7Bmax%7D%7D%2B%5Cfrac%7Bmv%5E2%7D%7B2%7D%5C%5C%0A%5Cfrac%7Bmv%5E2%7D%7B2%7D%3Dhc%28%5Cfrac%7B1%7D%7B%5Clambda%7D-%5Cfrac%7B1%7D%7B%5Clambda_%7Bmax%7D%7D%29%5C%5C%0Av%3D%5Csqrt%7B%5Cfrac%7B2hc%7D%7Bm%7D%28%5Cfrac%7B1%7D%7B%5Clambda%7D-%5Cfrac%7B1%7D%7B%5Clambda_%7Bmax%7D%7D%29%7D%5C%5C%0Av%3D%5Csqrt%7B%5Cfrac%7B2%2A6.63%2A10%5E%7B-34%7D%2A3%2A10%5E8%7D%7B9.1%2A10%5E%7B-31%7D%7D%28%5Cfrac%7B1%7D%7B380%2A10%5E%7B-9%7D%7D-%5Cfrac%7B1%7D%7B580%2A10%5E%7B-9%7D%7D%29%7D%3D%5C%5C%3D%5Csqrt%7B4.4%2A10%5E%7B5%7D%2A10%5E%7B9%7D%28%5Cfrac%7B1%7D%7B380%7D-%5Cfrac%7B1%7D%7B580%7D%29%7D%3D%5Csqrt%7B4.4%2A10%5E%7B14%7D%2A9%2A10%5E%7B-4%7D%7D%3D6.3%2A10%5E5+m%2Fs%5C%5C630km%2Fs)
Найдем скорость стержня при прохождении положения равновесия используя закон сохранения энергии: m*g*a*(1-cosa)=m*V^2/2
a- длина провода подвеса.
V=sqrt(2*g*a*(1-cosa)=sqrt(2*10*0,1*(1-0,87)=0,5 м/с
Разность потенциалов U=B*V*L=1*0,5*0,2=0,1 B
F=3 кН=3000 Н F=mg;→ m=F./g=3000/10=300 кг.
g=10 Н/кг
m=?