Question

Difficulty: MediumSimple Machines

A hydraulic press consists of a small effort piston of radius 2 cm2\text{ cm} and a large load piston of radius 8 cm8\text{ cm}. When an effort force of 50 N50\text{ N} is applied to the small piston, it successfully lifts a load of 600 N600\text{ N} placed on the large piston. What is the efficiency of this hydraulic press?

  1. 75%75\%Answer
  2. B
    133%133\%
  3. C
    33%33\%
  4. D
    25%25\%

Answer

The efficiency of the hydraulic press is 75%75\%.
The correct answer is 75%75\%. The mechanical advantage is MA=60050=12MA = \frac{600}{50} = 12, and the velocity ratio is VR=(82)2=16VR = \left(\frac{8}{2}\right)^2 = 16. Taking the ratio MAVR×100%\frac{MA}{VR} \times 100\% yields 1216×100%=75%\frac{12}{16} \times 100\% = 75\%.

Step-by-Step Solution

1
Calculate the Mechanical Advantage (MA) of the hydraulic press.
MA=LoadEffort=600 N50 N=12MA = \frac{\text{Load}}{\text{Effort}} = \frac{600\text{ N}}{50\text{ N}} = 12
Mechanical advantage measures the force multiplication factor of a machine.
2
Calculate the Velocity Ratio (VR) of the hydraulic press using the piston radii.
VR=Area of load pistonArea of effort piston=πR2πr2=(8 cm2 cm)2=42=16VR = \frac{\text{Area of load piston}}{\text{Area of effort piston}} = \frac{\pi R^2}{\pi r^2} = \left(\frac{8\text{ cm}}{2\text{ cm}}\right)^2 = 4^2 = 16
For a hydraulic press, velocity ratio equals the ratio of the cross-sectional areas of the pistons, which simplifies to the square of the radii ratio.
3
Compute the efficiency of the machine.
η=MAVR×100%=1216×100%=75%\eta = \frac{MA}{VR} \times 100\% = \frac{12}{16} \times 100\% = 75\%
Efficiency is defined as the ratio of Mechanical Advantage to Velocity Ratio expressed as a percentage.

Key Concept

Mechanical Advantage, Velocity Ratio, and Efficiency of a Hydraulic Press
Estimated Time:1m 30s
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