Physics
Figure shows a system of four pulleys. The upper two pulleys are fixed and the lower two are movable.
(a) Draw a string around the pulleys. Also show the point of application and direction in which the effort E is applied.
(b) What is the velocity ratio of the system?
(c) How are load and effort of the pulley system related?
(d) What assumption do you make in arriving at your answer in part (c)?
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Answer
(a) The diagram below shows the point of application and direction of the effort E:
(b) As we know that in a system of 4 pulleys, if the load moves up through a distance d, each segment of the string is loosened by a length d so the effort end moves through a distance 4 times d.
(c) As we know,
As M.A. = n = 4
Substituting the values in the formula we get,
(d) Assumptions made are —
(i) There is no friction in the pulley bearings.
(ii) Weight of lower pulleys is negligible.
(iii) The effort is applied downwards.
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