# Civil Engineering - Applied Mechanics

### Exercise :: Applied Mechanics - Section 3

46.

Pick up the incorrect statement from the following :

 A. The C.G. of a circle is at its centre B. The C.G. of a triangle is at the intersecton of its medians C. The C.G. of a rectangle is at the intersection of its diagonals D. The C.G. of a semicircle is at a distance of r/2 from the centre E. The C.G. of an ecllipse is at the intersection of axes.

Explanation:

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47.

A 49 kg lady stands on a spring scale in an elevator. During the first 5 sec, starting from rest, the scale reads 69 kg. The velocity of the elevator will be

 A. 10 m/sec B. 15 m/sec C. 20 m/sec D. 25 m/sec.

Explanation:

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48.

Pick up the correct statement from the following. A rubber ball when strikes a wall rebounds but a lead ball of same mass and velocity when strikes the same wall, falls down

 A. rubber and lead balls undergo equal changes in momentum B. change in momentum suffered by lead ball is less that of rubber ball C. momentum of rubber ball is less than that of lead ball D. none of these.

Explanation:

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49.

The instantaneous centre of a member lies at the point of intersection of two lines drawn at the ends of the member such that the lines are inclined to the direction of motion of the ends at

 A. 30° B. 45° C. 60° D. 90°

Explanation:

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50.

A rod 5 m in length is moving in a vertical plane. When it is inclined at 60° to horizontal, its lower end is moving horizontally at 3 m/sec and upper end is moving in vertical direction. The velocity of its upper end, is

 A. 0.5 m/sec B. 1.0 m/sec C. 1.5 m/sec D. 2.5 m/sec E. 3.0 m/sec