Q5. The screw of a jack is square threaded with two threads in a diameter of the screw is 5 cm. If centimetre . The outer the coefficient of friction is 0.1, calculate the force required to be applied at the end of the lever, which is 70 cm long (a) to lift a load of 4 kN, and (ii) to lower it
Answers
Explanation:
The load to be lifted is placed on the head of the screw. At the end of the handle, fitted to the screw head, an effort P is applied in the horizontal direction to lift the load W. The screw-jack works on the same principle on which an inclined plane works.
Let W = Weight placed on screw head,
P = Effort applied at the end of the handle,
L = Length of handle,
p = Pitch of the screw,
d = Mean diameter of the screw,
α = Angle of the screw or helix angle,
Φ = Angle of friction,
µ = Co-efficient of friction between screw and nut = tan Φ
When the handle is rotated through one complete turn, the screw is also rotated through one turn. Then the load is lifted by a height p (pitch of screw).
The development of one complete turn of a screw thread is shown in Fig. 3.49 (a). This is similar to the inclined plane. The distance AB will be equal to the circumference (πd) and distance BC will be equal to the pitch (p) of the screw. From the Fig. 3.49 (a), we have
Answer:
same answer
Explanation:
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