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4

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

Correct Answer :

C. 20 m/sec


Related Questions

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4

The C.G. of the shaded area of the below figure whose curve OM is a parabola from y-axis, is

A. a/4

B. 3a/4

C. 3b/10

D. 3a/10

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4

The resultant of two forces P and Q acting at an angle θ, is

A. P2 + Q2 + 2P sin θ

B. P2 + Q2 + 2PQ cos θ

C. P2 + Q2 + 2PQ tan θ

D. √(P2 + Q2 + 2PQ cos θ)

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4

When two forces, each equal to P, act at 90° to each other, then the resultant will be

A. P

B. P√2

C. P/√2

D. 2P

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4

For a simple pendulum, the period of one oscillation is

A. 2π √(l/2g)

B. 2π √(2g/l)

C. 2π √(l/g)

D. 2π √(g/2l)

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4

One Newton force, is

A. 103 dynes

B. 104 dynes

C. 105 dynes

D. 106 dynes

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4

Joule is the unit of

A. Power

B. Impulse

C. Work

D. Momentum

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4

For a given velocity of a projectile, the range is maximum when the angle of projection is

A. 30°

B. 45°

C. 90°

D.

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4

The centre of gravity of a triangle is at the point where three

A. Medians of the triangle meet

B. Perpendicular bisectors of the sides of the triangle meet

C. Bisectors of the angle of the triangle meet

D. None of these

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4

A ball which is thrown upwards, returns to the ground describing a parabolic path during its flight

A. Vertical component of velocity remains constant

B. Horizontal component of velocity remains constant

C. Speed of the ball remains constant

D. Kinetic energy of the ball remains constant

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4

A cube on a smooth horizontal surface

A. Cannot be in stable equilibrium

B. Cannot be in neutral equilibrium

C. Cannot be in unstable equilibrium

D. Can be in any of these states

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4

The length of a Second's pendulum, is

A. 99.0 cm

B. 99.4 cm

C. 100 cm

D. 101 cm

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4

A simple pendulum of length 1 has an energy E when its amplitude is A. If its amplitude is increased to 2 A, the energy becomes

A. E

B. E/2

C. 2E

D. 4E

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4

Two forces act an angle of 120°. If the greater force is 50 kg and their resultant is perpendicular to the smaller force, the smaller force is

A. 20 kg

B. 25 kg

C. 30 kg

D. 35 kg

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4

A ladder of weight 'w' rests against a smooth vertical wall, and rests on rough horizontal ground, the coefficient of friction between the ladder and the ground being 1/4. The maximum angle of inclination of the ladder to the vertical, if a man of weight 'w' is to walk to the top of it safely, is tan'1 x, where x is

A. 1/4

B. 1/3

C. 3

D. 4

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4

A string of length 90 cm is fastened to two points A and B at the same level 60 cm apart. A ring weighing 120 g is slided on the string. A horizontal force P is applied to the ring such that it is in equilibrium vertically below B. The value of P is:

A. 40 g

B. 60 g

C. 80 g

D. 100 g

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4

If the angular distance, 0 = 2t3 - 3t², the angular acceleration at t = 1 sec. is

A. 1 rad/sec²

B. 4 rad/sec²

C. 6 rad/sec²

D. 12 rad/sec²

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4

The equation of motion of a particle starting from rest along a straight line is x = t3 - 3t2+ 5. The ratio of the accelerations after 5 sec and 3 sec will be

A. 2

B. 3

C. 4

D. 5

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4

If G is the Gauge of track, v is velocity of the moving vehicle, g is the acceleration due to gravity and r is the radius of a circular path, the required super elevation is

A. gv²/Gr

B. Gr²/gr

C. Gr²/gv²

D. Gv²/gv

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4

If a particle moves with a uniform angular velocity ω radians/sec along the circumference of a circle of radius r, the equation for the velocity of the particle, is

A. v = ω √(y² - r²)

B. y = ω √(y - r)

C. v = ω √(r² + y²)

D. v = ω √(r² - y²)

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4

The velocity ratio of the differential wheel and axle is

A. R/r1 - r2

B. 2R/r1

C. 3R/r1 - r2

D. 2R/r1 + r2

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4

According to Kennedy's theorem, if three bodies have plane motions, their instantaneous centres lie on

A. A point

B. A straight line

C. Two straight lines

D. A triangle

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4

A particle executes a simple harmonic motion. While passing through the mean position, the particle possesses

A. Maximum kinetic energy and minimum potential energy

B. Maximum kinetic energy and maximum potential energy

C. Minimum kinetic energy and maximum potential energy

D. Minimum kinetic, energy and minimum potential energy

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4

The reaction at the central support B of the beam ABC hinged at D shown in below figure is

A. 2 t

B. 5.8 t

C. 0.2 t

D. 3.5 t

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4

Energy may be defined as

A. Power of doing work

B. Capacity of doing work

C. Rate of doing work

D. All the above

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4

If α and u are the angle of projection and initial velocity of a projectile respectively, the horizontal range of the projectile, is

A. u² sin α/g

B. u² sin² α/g

C. u² sin α/2g

D. u² sin² α/2g

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4

A 50 kg boy climbs up a 8 m rope in gymnasium in 10 sec. The average power developed by the boy is approximately

A. 400 watts

B. 500 watts

C. 4000 watts

D. None of these

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4

It is observed that in a certain sinusoidal oscillation, the amplitude is linearly dependent on the frequency f. If the maximum velocity during the oscillation is V, then V must be proportional to

A. f

B. 1/f

C. 1/f²

D.

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4

The member which does not carry zero force in the structure shown in below figure, is

A. ED

B. DC

C. BC

D. BD

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4

A projectile is fired with a velocity of 100.3 m/sec. at an elevation of 60°. The velocity attained by the projectile when it is moving at a height of 100 m, is

A. 70 m/sec

B. 75 m/sec

C. 80 m/sec

D. 90 m/sec

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4

The acceleration of a train starting from rest at any instant is 1/6(V + 1) m/sec² where V is the velocity of the train in m/sec. The train will attain a velocity of 36 km/hour after travelling a distance of

A. 2000 m

B. 2100 m

C. 2200 m

D. 2300 m