Questions 11–20 of 72. Imported answers require independent review unless marked reviewed.

Topic practice 72 questionsPage 2 of 8

Question 77

Open question
XE-DMCQ2 marksNeeds review
The figure shows a rod PQ, hinged at P, rotating counter-clockwise with a uniform angular speed of 15 rad/s. A block R translates along a slot cut in rod PQ. At the instant shown the distance PR = 0.5 m and

. The relative velocity of R with respect to the rod PQ is 5 m/s at the instant shown. The relative acceleration of R with respect to the rod PQ is zero at the instant shown.
Which one of the following is the CORRECT magnitude of the absolute acceleration (in m/s

) of block R?
Diagram for Engineering Sciences question 77

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Question 78

Open question
XE-DMCQ2 marksNeeds review
The frame shown in the figure is loaded at S with a force of 2000 N. The reactions at T are denoted by T

and T

, while the reaction at W is W

. Neglect the weight of the members.
Which one of the following options for the magnitudes of the forces (in N), T

, T

and W

, is CORRECT?
Diagram for Engineering Sciences question 78

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Question 86

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XE-DNAT2 marksNeeds review
An electric motor’s rotor is spinning at 1500 rpm when its load and power are cut-off. The rotor which has a mass of 50 kg and a radius of gyration of 200 mm, then coasts down to rest. Due to kinetic friction, a constant torque of 10 Nm acts on the rotor as it coasts down. The number of revolutions executed by the rotor before it comes to rest is ____ (in integer).

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Question 67

Open question
XE-DMCQ1 markNeeds review
An L-shaped rigid member is fixed at the midpoint of a simply-supported beam, as shown in figure (i). The member is subjected to a vertically downward force P at its free end. In an equivalent system, the member along with the applied load is replaced with a force Q = P and a moment M (see figure (ii)). Which of the following statements is correct?
(Negelect the mass of the beam and of the rigid member)
Diagram for Engineering Sciences question 67

Diagram for Engineering Sciences question 67 (figure 2)

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Question 68

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A block of weight W, placed on a surface, is subjected to a horizontal force P as shown in the figure. The line of action of force P passes through the center-of-gravity of the block. The magnitude of P is such that the block remains at rest. If N is the resultant normal reaction exerted by the surface, and F is the frictional force acting on the bottom surface of the block, then which of the following represents the correct free body diagram of the block?
Diagram for Engineering Sciences question 68

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Question 71

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An ice-skater starts spinning during her performance. As she retracts her arms and legs closer to her body, her angular velocity ____________________.
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Question 74

Open question
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A particle of mass 1 kg is attached to one end of a spring having stiffness of 125 N/m. The free length of the spring is 100 mm. The system is rotated about the other end of the spring at a uniform angular velocity of 5 rad/s. Ignore gravity and consider that the elongation of the spring may be comparable to the free length of the spring. The elongation of the spring (in mm, rounded off to the nearest integer) is _____ .

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Question 77

Open question
XE-DMCQ2 marksNeeds review
A pin-jointed truss has a pin support at the point E and a roller support at the point F. A horizontal force P is applied at pin H as shown in the figure. Which one of the members is in compression?
Diagram for Engineering Sciences question 77

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Question 78

Open question
XE-DMCQ2 marksNeeds review
Two identical rigid slender bars of length

and mass

are acted upon by a transverse force F at one of the ends as shown in the figure. In the first case, the bar is pinned at the other end. In the second case, the bar is pinned at its mid-point. What should be the magnitude of the force F such that the resulting angular accelerations of the two bars are equal?
Diagram for Engineering Sciences question 78

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Question 85

Open question
XE-DNAT2 marksNeeds review
A turn-table is rotating about its center with an angular velocity of 2 rad/s in the counter-clockwise direction. There is a groove in the turn-table within which a marble moves with a constant speed

m/s relative to the turn-table. At a given instant, the marble is at a radial distance of 1 m from the center and the line joining the center of the turn-table with the marble makes an angle of 30° with the groove. The value of

(in m/s, rounded off to one decimal place) for which there is no radial acceleration for the marble at this instant is _____.
Diagram for Engineering Sciences question 85


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