tailieunhanh - Physics exercises_solution: Chapter 06

Bộ tài liệu bài tập tham khảo môn vật lý bậc đại học bằng tiếng anh Chapter 06 | a b N c J - . a Pulling slowly can be taken to mean that the bucket rises at constant speed so the tension in the rope may be taken to be the bucket s weight. In pulling a given length of rope from Eq. W Fs mgs kg m s2 m J. b Gravity is directed opposite to the direction of the bucket s motion so Eq. gives the negative of the result of part a or - 265 J . c The net work done on the bucket is zero. 300J. a The friction force to be overcome is f Mk n juk mg s2 N or 74 N to two figures. b From Eq. Fs N m 331J . The work is positive since the worker is pushing in the same direction as the crate s motion. c Since f and s are oppositely directed Eq. gives - fs - N m -331J. d Both the normal force and gravity act perpendicular to the direction of motion so neither force does work. e The net work done is zero. a See Exercise . The needed force is r mg 30kg s2 F --------------- ------------------------- N cos 0- ksin cos30 - sin30 keeping extra figures. b Fscos0 N cos 30 J again keeping an extra figure. c The normal force is mg F sin0 and so the work done by friction is - m 30 kg m s2 sin30 . d Both the normal force and gravity act perpendicular to the direction of motion so neither force does work. e The net work done is zero. From Eq. Fscos b 180N 300 m x 104 J. 2Fscos0 2 x 106 N x 103 m cos14 x 109 J or x 109 J to two places. The work you do is F- i 30N i - 40N j i - j 30N -40N -270N m 120N m -150J a i Tension force is always perpendicular to the displacement and does no work. ii Work done by gravity is - mg y2 - yj. When y y2 Wmg 0 . b i Tension does no work. ii Let lbe the length of the string. Wmg -mg y2 -y1 -mg 2 J The displacement is upward and the .

TỪ KHÓA LIÊN QUAN
TÀI LIỆU MỚI ĐĂNG
65    94    0    29-05-2024
crossorigin="anonymous">
Đã phát hiện trình chặn quảng cáo AdBlock
Trang web này phụ thuộc vào doanh thu từ số lần hiển thị quảng cáo để tồn tại. Vui lòng tắt trình chặn quảng cáo của bạn hoặc tạm dừng tính năng chặn quảng cáo cho trang web này.