A screw jack with a Tommy bar of length 12cm is used to raise a car through a vertical height of 25cm by turning the Tommy bar through 50 revolutions. Calculate the approximate velocity ratio of the jack [(pi = 3.142)]
-
A.
21 -
B.
38 -
C.
48 -
D.
151
Correct Answer: Option D
Explanation
P = (frac{25}{50} = 0.5)
V.R = (frac{2pi D}{p} = frac{2 times 3.142 times 12}{0.5})
= 151