По шероховатой горизонтальной поверхности тянут за веревку груз m=1кг с постоянной скоростью v=0, 1 п/с. найдите мощность силы натяжения веревки, если угол между горизонталью и направлением веревки равен 30 градусов, а коэффициент трения между грузом и поверхностью равен 0.1. и рисунок

Найдем силу тяги f тяги =f тр    так как    скорость постоянная f тр= k*n    n= m*g - fтяг*sina fтяг= k*m*g- k*f тяг*sina f тяг= k*m*g/(1+k*sina)=0,1*1*10/0,15=6,7 н найдем мощность по формуле p=  fтяг*v=6,7*0,1=0,67 вт

Exercise 1 1. they often make sandwiches for lunch. 2. i am not study at the moment. 3. i never study at night. 4. she talks to her friends every day. 5. she is not talking to her friends at the moment. 6. we have lessons every day. 7. we are not having an english lesson now. 8. he usually plays with jim or henry. exercise 2 1. the telephone rang while i was having a hot shower. 2. when you phoned last night, i was reading a fantastic book. 3. mary and i saw henry while we were waiting for the bus this morning. 4. last night we were having dinner with friends when helen arrived. 5. while the teacher explained the problem, lisa was dropping her books.

S=1,2*15 cм²=18 см²=             плотность тока: j=i/s;   =0,0018 м²=1,8 10⁻³ м²                                       j=3,6 10⁻³/1,8 10⁻³=2 а/м². =3.6 ма=3,6 10⁻³ а                                         ответ: j=2 а/м². j-?