Theory of Machine
Which one of the following is an exact straight line mechanism using lower pairs?

Peaucellier’s mechanism
Robert’s mechanism
Grasshopper mechanism
Watt’s mechanism

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Theory of Machine
The displacement of the reciprocating roller follower, when it has contact with the straight flanks of the tangent cam, is given by (where r₁ = Minimum radius of the cam, r₂ = Radius of the roller follower, and θ = Angle turned by the cam from the beginning of the follower displacement)

(r₁ + r₂) (1 + cosθ)
(r₁ - r₂) [(1 - cosθ)/cosθ]
(r₁ - r₂) (1 - cosθ)
(r₁ + r₂) [(1 - cosθ)/cosθ]

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Theory of Machine
In a steam engine, one method of obtaining the earlier cut-off with a simple slide valve is by increasing the angle of advance of the eccentric while the throw of the eccentric, steam lap and exhaust lap are kept constant. This method will

Reduce length of effective stroke of piston
All of these
Cause withdrawing or throttling of steam
Reduce maximum opening of port to steam

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