tailieunhanh - Physics exercises_solution: Chapter 09

Bộ tài liệu bài tập tham khảo môn vật lý bậc đại học bằng tiếng anh Chapter 09 | a rad . m b cm r cm. 128 n rad 180 c m m. x rev 2n rad V 1min a 11900----------------------------------Ixl-II-I 199rad s. V min V rev V 60s b 35 x rad 180 199 rad s x 10 3 s. a a L C rad s3 t so at t s a 42 rad angular acceleration dt is proportional to the time so the average angular acceleration between any two times is the arithmetic average of the angular accelerations. b rnz rad s3 t2 so at t s rnz rad s. The angular velocity is not linear function of time so the average angular velocity is not the arithmetic average or the angular velocity at the midpoint of the interval. a a t y -2fit s3 t. Z dt b az s rad s3 s rad s2. a - M - rad s - rads -2 40 2. av-z s s . which is half as large in magnitude as the acceleration at t s. a rnz y 3 t2 s rad s3 t2 b At t 0 rnz y O zlflfl rorl c A t OOc m 1 Q rorl c f Q O ro crt 70 t Qid c s. c At t s uj iad s v iad so av-z 5 00s 0. 0iad s. The acceleration is not constant but increasing so the angular velocity is larger than the average angular velocity. rnz 250 rad s - rad s2 t - rad s3 t2 az - rad s2 - s3 t. a Setting rnz 0 results in a quadratic in t the only positive time at which o. 0 is t . b At t s az s2. c At t s Q 586 rad rev. d At t 0 o. 250rad s. e mav-z -8 138 rad s. 9 ft dQ __ 2 dwz r 7 _ zCxiV n r zy O D . a c z dt 2bt 3ct and 2D 6ct. b setting 0 t - z. a The angular acceleration is positive since the angular velocity increases steadily from a negative value to a positive value. b The angular acceleration is a - - s 2 00 rad s2 t s Thus it takes seconds for the wheel to stop z 0 . During this time its speed is decreasing. For the next s its speed is increasing from 0 rad s to rad s. c We have Q 00 0t 2 .