1 Question (a) what is meant by mechanical advantage? Show how simple levers and

Question

1 Question (a) what is meant by mechanical advantage? Show how simple levers and four-bar linkages can be used to amplify an input force. the mechanism shown in Figure 1b calculate the increase in mechanical 15l (b) advantage as a decreases from 10 to 0° Figure Q1b (c) Calculate the mechanical advantage for each of the five pulley systems shown in Figure Qlc. If w is 100 kg what is the value of P in each case? Neglect frictional 151 effects. Figure Q1c d) Briefly describe each of the following using sketches to illustrate your answer where necessary: ratchet mechanism; Geneva wheel mechanism, slider-crank, Robert's straight line mechanism, Hooke or Cardan joint.

Explanation / Answer

(a) Mechanical advantage is the ratio between the force produced by the machine respective to the force applied to it. It is used in assessing the performance of the machine.

Thus MA=Resultant force / Applied force

For a lever, Load x load arm= Effort x Effort arm, since MA= Load / Effort =Effort arm/ load arm

if effort arm is greater than load arm, lever is amplifying the force.

Crank-shaft is a case of 4-bar mechanism,

Here, small rotary motion produced by piston rods is converted by crank-shaft into large rotary motion of the engine flywheel.

(b) From the diagram by resolving forces along one of the arm,

P cos(a)=Fcos(90-a)=Fsin(a).....as the arm is incompressible

therefore, P=F tan(a)

Thus Mechanical Advantage= Load / Effort = F/P= cot(a).....by substituting value of P from above

MA=cot(10)=5.67 (for a=10o)

MA=cot(0)=not defined....thus no advantage. (for a=0o)

(c) if w=100kg ....Let T be the tension in each string.

For A, T=w and T=P, MA=w/P=T/T=1 therefore P=100kg

For B, 2T=w and T=P, MA=w/P=2T/T=2 therefore P=50kg

For C, 3T=w and T=P, MA=w/P=3T/T=2 therefore P=33.3kg

For D, 4T=w and T=P, MA=w/P=4T/T=4 therefore P=25kg

For E, 5T=w and T=P, MA=w/P=5T/T=5 therefore P=10kg

(d) please refer your textbook. It would be too long to describe each of them here.

Related Questions

Navigate

• Browse (All)
• Browse 1
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.