A body of mass 7.5 kg is to be pulled along a plane which is inclined at 30º to the horizontal. If the efficiency of the plane is 75%, what is the minimum force required to pull the body up the plane?
A
20.0N
B
50.0N
C
75.0N
D
5.0N
Verified Correct Answer: B.
Step-by-Step Mathematical Solution
Efficiency = \(\frac{\text{MA}{\text{VR}}\) x 100
But V.R = \(\frac{1}{sin\theta}\) = \(\frac{1}{sin 30}\) = 2
M.A = \(\frac{\text{L}}{\text{E}}\)
Efficiency = \(\frac{\text{MA}{\text{VR}}\) x 100
0.75 = \(\frac{\text{M.A}}{2}\)
0.75 x 2 = M.A
M.A = 1.5 = \(\frac{7.5 x 10}{\text{E}}\)
1.5E = 75
E = \(\frac{75}{1.5}\) = 50N
Source: WAEC / JAMB / NECO Classroom Archive (Record #76332)