Question

The position of the automobile jack shown is controlled by a screw ABC that is single threaded at each end (right-handed thread at A, left-handed thread at C). Each thread has a pitch of 2.5 mm and a mean diameter of 10 mm. If the coefficient of static friction is 0.15, determine the magnitude of the couple M that must be applied to raise the automobile.

3500 N D С М А 30° В 30° E

Answer 1

Sol4 Ham; Draw FBD diagram. 3500 N I 30 30° FOD FAD Since Otis Symmetry the force om memben AD is equal to farce am memben CD FAID = FD Restoving the farce alang y-axis FAQ Sin 30 + Fco Sin 30 – 3500 = 0 2 fro Sin 30 – 3500 =0 FAD = FCD = 3 500 N Draw FBD at paint a Pep. D Since gtis gymmetry FCE a Fed Resolving fance alang y-aris Efn=0 FLE Cop 30° + FD Corso - Pacco 3500 COD 30 + 3500 COD 30 - FALCO FAC 3 60 62 . 1778 N Draw the block II URL OLE I am tanco P -) Ostan -1/ PI I dm TT d.m Bz tem"( 205 ) = 415499 17X16 / se tomtu) = tan (0.15) = 0.530 tan (@+48) = FAC }ám (4.548 & s3) = 8 6062.1778 Q = 1408.37 M Since then one two screws the couple will be double M = 2 Grm = 2x 1408-373 = 12675.338 N-mm = 42 - 67s N - M .. magnitude of of the couple that must be applied to use the automobile in 12.675 N-m)

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