A pilot flies a small plane in a vertical loop of radius r. At the top of its trajectory he experiences weightlessness. If the acceleration due to gravity is g, the speed of the plane at the top of its trajectory would be
Zero
Infinite
gr
2gr
Correct Answer :
C. gr
Related Questions
Two circular discs of same weight and thickness are made from metals having different densities. Which disc will have the larger rotational inertia about its central axis?
Disc with larger density
Disc with smaller density
Both discs will have same rotational inertia
None of the above
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 mechanical advantage of the lifting machine is
15
18
20
26
The reaction at the support B of the beam shown in below figure is 
1.6 t
9.6 t
8.5 t
0.5 t
A satellite moves in its orbit around the earth due to
Gravitational force
Centripetal force
Centrifugal force
None of these
A stone was thrown vertically upwards from the ground with a velocity of 50 m/sec. After 5 seconds another stone was thrown vertically upwards from the same place. If both the stones strike the ground at the same time, then the velocity with which the second stone was thrown should be (Assume g = 10 m/sec²)
15 m/sec
25 m/sec
40 m/sec
50 m/sec
The ratio of the reactions RA and RB of a simply supported beam shown in below figure is 
0.50
0.40
0.67
1.00
Lami's theorem states that
Three forces acting at a point are always in equilibrium
If three forces acting on a point can be represented in magnitude and direction by the sides of a triangle, the point will be in the state of equilibrium
Three coplanar forces acting at a point will be in equilibrium, if each force is proportional to the sine of the angle between the other two
Three coplanar forces acting at a point will be in equilibrium if each force is inversely proportional to the sine of the angle between the other two
Ball A of mass 250 g moving on a smooth horizontal table with a velocity of 10 m/s hits an identical stationary ball B on the table. If the impact is perfectly elastic, the velocity of the ball B just after impact would be
Zero
5 m/sec
10 m/sec
None of these
M.I. of solid sphere, is
Mr2
½ Mr2
Mr2
πr4/2
The vertical reaction at the support A of the structure shown in below figure, is 
1 t
2 t
3 t
3.5 t
A weight W is suspended at the free end of a light member hinged to a vertical wall. If the angle of inclination of the member with the upper wall is θ°, the force introduced in the member, is
W sec θ
W cos θ
W sin θ
W cosec θ
A stone of mass 1 kg is tied to a string of length 1 m and whirled in a horizontal circle at a constant angular speed 5 rad/sec. The tension in the string is,
5 N
10 N
15 N
25 N
If the tension in a cable supporting a lift moving upwards is twice the tension when the lift is moving downwards, the acceleration of the lift, is
g/2
g/3
g/4
g/5
Free body diagram is an
Isolated joint with only body forces acting on it
Isolated joint with internal forces acting on it
Isolated joint with all the forces, internal as well as external, acting on it
None of the above
When two forces, each equal to P, act at 90° to each other, then the resultant will be
P
P√2
P/√2
2P
If two forces of 3 kg and 4 kg act at right angles to each other, their resultant force will be equal to
7 kg
1 kg
5 kg
None of these
Impulse can be obtained from a
Force-displacement diagram
Force-time diagram
Velocity-time diagram
Velocity-displacement diagram
Joule is the unit of
Work
Force
Power
Torque
The unit of moments in M.K.S system, is
kg.m
kg/m2
kg/sec2
kg/sec
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
9.3 m/sec
8.3 m/sec
7.3 m/sec
6.3 m/sec
The shape of a suspended cable for a uniformly distributed load over it is
Circular
Parabolic
Catenary
Cubic parabola
The resultant of two forces acting at right angles is √34 kg and acting at 60° is 70 kg. The forces are
1 kg and 4 kg
2 kg and 3 kg
√3 kg and √5 kg
3 kg and 5 kg
The moment of inertia of a circular lamina of diameter d, about an axis perpendicular to the plane of the lamina and passing through its centre, is
πd4/12
πd4/16
πd4/24
πd4/32
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
50
55
60
65
Which one of the following laws is not applicable to a simple pendulum?
The time period does not depend on its magnitude
The time period is proportional to its length l
The time period is proportional to l, where l is length
The time period is inversely proportional to g, where g is the acceleration due to gravity
The bending moment in an arch is proportional to
Vertical ordinate of funicular polygon
Vertical ordinate of the arch
Intercept between the arch axis and the funicular polygon
None of these
The resultant of two forces P and Q acting at an angle θ, is
P2 + Q2 + 2P sin θ
P2 + Q2 + 2PQ cos θ
P2 + Q2 + 2PQ tan θ
√(P2 + Q2 + 2PQ cos θ)
A stone is thrown vertically upwards with a vertical velocity of 49 m/sec. It returns to the ground in
5 sec
8 sec
10 sec
20 sec
For a non-concurrent force system to be in equilibrium
Only the closure of force polygon is sufficient
Only the closure of funicular polygon is sufficient
Both force polygon and funicular polygon must close
None of the above
From the circular plate of a diameter 6 cm is cut out a circular plate whose diameter is equal to radius of the plate. The C.G. of the remainder shifts from the original position through
0.25 cm
0.50 cm
0.75 cm
1.00 cm