A 49 kg lady stands on a spring scale in an elevator. During the first 5 sec, st

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

Correct Answer

20 m/sec

Applied Mechanics problems

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2. Principle of Transmissibility of Forces states that, when a force acts upon a body, its effect is
Options
A. maximum if it acts at the centre of gravity of the body
B. different at different points on its line of
C. same at every point on its line of action
D. minimum if it acts at the C.G. of the body
E. none of these.

3. The necessary condition of equilibrium of a body, is :
Options
A. algebraic sum of horizontal components of all the forces must be zero
B. algebraic sum of vertical components of all the forces must be zero
C. algebraic sum of the moments of the forces about a point must be zero
D. all (a), (b) and (c).

4. P is the force acting on a body whose mass is m and acceleration is f. The equation P - mf = 0, is known as
Options
A. equation of dynamics
B. equation of dynamic equilibrium
C. equation of statics
D. none of these.

5. A number of forces acting simultaneously on a particle of a body
Options
A. may not be replaced by a single force
B. may be replaced by a single force
C. may be replaced by a single force through C.G. of the body
D. may be replaced by a couple
E. none of these.

6. Two particles have been projected at angles 64� and 45� to the horizontal. If the velocity of projection of first is 10 m/sec, the velocity of projection of the other for equal horizontal ranges is
Options
A. 9.3 m/sec
B. 8.3 m/sec
C. 7.3 m/sec
D. 6.3 m/sec.

8. Pick up the incorrect statement from the following :
Options
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.

9. The moment of inertia of a hollow circular section whose external diameter is 8 cm and internal diameter is 6 cm, about centroidal axis, is
Options
A. 437.5 cm⁴
B. 337.5 cm⁴
C. 237.5 cm⁴
D. 137.5 cm⁴
E. 37.5 cm⁴.

10. A load of 500 kg was lifted through a distance of 13 cm. by an effort of 25 kg which moved through a distance of 650 cm. The velocity ratio of the lifting machine is
Options
A. 50
B. 55
C. 60
D. 65
E. 70.

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