Опубликовано 1 год назад по предмету Физика от sscTuataro

При торможении мотоцикла массой 400 кг на него действует сила трения, равная по модулю 1000 Н. Най-ти время, необходимое для полной остановки мотоцикла, если работа силы трения, совершаемая при этом, равна -20 кДж.

  1. Ответ
    Ответ дан WordSnot
    m=400 кгFтр=1000 НA=-20 кДж=-20000 Джt=?В данном случае, работа силы трения, совершенная мотоциклом, равна кинетической энергии мотоцикла:[tex]A= frac{mv^{2} }{2} [/tex]К этой формуле мы еще вернемся. Сейчас посмотрим, есть ли у нас достаточно величин для того, чтобы найти нужное нам время:[tex]t= frac{v}{a} [/tex] Нет ни ускорения, ни скорости. Скорость мы уже можем найти, зная работу:[tex]v= sqrt{ frac{2A}{m} } [/tex] = корень из 100 = 10 м/с.Ускорение было вызвано силой трения, которую в соответствии со вторым законом Ньютона можно записать в виде F=ma, следовательно:[tex]ma=еmg[/tex][tex]a=еg[/tex]Возвращаемся к формуле времени:[tex]t= frac{ sqrt{frac{2A}{m} } }{еg} = frac{ Fsqrt{frac{2A}{m} } }{Ng} [/tex] = [tex]t= frac{ sqrt{frac{2A}{m} } }{еg} = frac{ Nsqrt{frac{2A}{m} } }{Fg} [/tex] = [tex] frac{Nv}{Fg} [/tex] = 4 с.Ответ: время, необходимое для полной остановки мотоцикла, равно 4 с.
    1. Ответ
      Ответ дан WordSnot
      Сорри, там, где буква е - я хотел написать k, редактор не распознал)
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