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UPSC Physics prepare Q&A

4151.A body is moving along a circular path with variable speed. It has
a radial acceleration
a tangential acceleration
zero acceleration
both tangential and radial accelerations
4152.A body is traveling in a circle at constant speed. It
has constant velocity.
has no acceleration
has an inward acceleration
has an outward radial acceleration
4153.A body of mass 500 gram is rotating in a vertical circle of radius 1 m. What is the difference in its kinetic energies at the top and the bottom of the circle
4.9 J
19.8 J
2.8 J
9.8 J
4154.A bucket containing water is tied to one end of a rope of length 2.5 m and rotated about the other end in a vertical circle. What should be the minimum velocity of the bucket at the highest point, so that the water in the bucket will not spill? (g = 10 m/s2)
2.5 m/s
4 m/s
5 m/s
7 m/s
4155.A bucket tied at the end of a 1.6 m long string is whirled in a vertical circle with a constant speed. What should be the minimum speed so that the water from the bucket does not spill when the bucket is at the highest position
4 m/sec.
6.25 m/sec.
16 m/se
None of these
4156.A can filled with water is revolved in a vertical circle of radius 4 metre and the water does not fall down. The time period of revolution will be
1 sec
10 sec
8 sec
4 sec
4157.A car is moving in a circular track of radius 10 metre with a constant speed of 10 m/sec. A plumb bob is suspended from the roof of the car by a light rigid rod of 1 metre long. The angle made by the rod with the track is
zero
30°
45°
60°
4158.A car is moving in horizontal circular track of radius 10 m, with a constant speed of 36 km/hour. A simple pendulum is suspended from the roof of the car. If the length of the simple pendulum is 1 m, what is the angle made by the string with the track
30°
45°
60°
90°
4159.A car is moving on a circular path and takes a turn. If R1 and R2 are the reactions on the inner and outer wheels respectively, then
R1 = R2
R1 < R2
R1 > R2
R1 ≥ R2
4160.A car is moving with a speed of 30 m/s on a circular path of radius 500 m. Its speed is increasing at the rate of 2 m/s2. The acceleration of the car is
9.8 m/s2
1.8 m/2
2 m/s2
2.7 m/s2
4161.A car moving on a horizontal road may be thrown out of the road is taking a turn
by the gravitational force
due to the lack of proper centripetal force
due to the lack of frictional force between the tire and the road
due to the reaction of the ground
4162.A car of mass 1000 kg moves on a circular road with a speed of 20 m/s. Its direction changes by 90° after traveling 628 m on the road. The centripetal force acting on the car is
500 N
1000 N
1500 N
2000 N
4163.A car of mass 800 kg moves on a circular track of radius 40 m. If the coefficient of friction is 0.5, then maximum velocity with which the car can move is
7 m/s
14 m/s
8 m/s
12 m/s
4164.A car sometimes overturns while taking a turn. When it overturns, it is
the inner wheel which leaves the ground first
the outer wheel which leaves the ground first
both the wheel leave the ground simultaneously
either inner wheel or the outer wheel leaves the ground
4165.A coin kept on a rotating gramophone disc just begins to slip if its centre is at a distance of 8 cm from the centre of the disc. The angular velocity of the gramophone disc is then doubled. Through what distance, the coin should be shifted towards the centre, so that the coin will just slip
2 cm
4 cm
6 cm
16 cm
4166.A cyclist goes round a circular path of circumference 343 m in s. The angle made by him, with the vertical is
42°
43°
44°
45°
4167.A cyclist turns around a curve at 15 miles per hour. If he turns at double the speed, the tendency of overturn is
doubled
quadrupled
halved
unchanged
4168.A fighter aeroplane flying in the sky dives with a speed of 360 km/hr in a vertical circle of radius 200 m. Weight of the pilot sitting in it is 75 kg. What will be the value of force with which the pilot presses his seat when the aeroplane is at highest position (g = 10 m/s2)
3000 N
1500 N
(75 × g)N
300 N
4169.512 calories of radiation is incident on a body. It absorbs 220 calories the coefficient of emission is
0.43
0.57
1.7
0.34
4170.Heat energy received by the earth from the sun is due to
Convection
Radiation
Reflection of light
Transmission of light
4171.Two stars A and B radiate maximum energy at 3600°A and 3600°A respectively. Then the ratio of absolute temperatures of A and B is
256: 81
81: 256
3: 4
4: 3
4172.Emissivity of perfectly black body is
1
2
5
0
4173.Absorptive power of perfectly black body is
Zero
Infinity
One
Constant
4174.Newton’s law of cooling is also applicable to
Convection losses
Natural convection losses
Forced convection losses
None of the above
4175.Which of the following statement is wrong
Rough surfaces are better radiators tan smooth surfaces
Highly polished mirror surfaces are very good radiators
Black surfaces are better absorbers then white ones
Black surfaces are better radiators then white ones
4176.The best ideal black body is
Lamp of charcoal heated to high temperature
Metal coated with a black dye
Glass surface coated with coalter
Hollow enclosure blackened inside and having a small hole
4177.The earth intercepts approximately one billionth of the power radiated by the sun. if the surface temperature of the sun were to drop by a factor of 2, the average radiant energy incident on earth per second would reduce by factor of
2
4
8
16
4178.If the temperature of the sun is doubled. The rate of energy received on the earth will be increased by a factor of
2
4
8
16
4179.A body in a room cools from 90°C to 80°C in 5 minutes. the time taken to cool from 70°C to 60°C is
Less than 5 minute
5 minute
More than 5 minutes
Less or more than 5 minutes depending upon the nature of the body
4180.A sphere, a cube and a thin circular plate, all made of the same material and having the same mass are initially heated to a temperature of 3000°K, which of these will cool fastest
Sphere
Cube
Plate
None
4181.The temperature of a piece of metal is raised from 27°C to 51.2°C. the rate at which metal radiates energy increases nearly
1.36 times
2.36 times
3.36 times
4.36 times
4182.A cup of tea cools from 80°C to 60°C in one minute. The ambient temperature is 30°C. in cooling from 60°C to 50°C, it will take
50 sec
90 sec
60 sec
30 sec
4183.Spectrum of a perfectly black body is
Line spectrum
Band spectrum
Continuous spectrum
None of these
4184.An object is at the temperature of 400°C. at what temperature would it radiant energy twice as first? The temperature of surrounding may be assumed to be negligible
200°C
200°K
800°C
800°K
4185.The process of heat transfer in which heat is transferred with actual migration of medium particles is known as
Conduction
Convection
Radiation
Reflection
4186.Which of the following is most repaid process
Conduction
Convection
Radiation
None of these
4187.Which of the following will radiate heat to large extent?
Rough surface
Polished surface
Black rough surface
Black polished surface
4188.The rate of radiation of black body at 0°C is E watt. The n the rate of radiation of this black body at 273°C will be
16 E
8 E
4 E
E
4189.Woolen clothes keep the body warm, because wool
Is a bad conductor
Increases the temperature of body
Decreases the temperature
All of these
4190.The good absorber of heat are
Non-emitter
Poor-emitter
Good-emitter
Highly polished
4191.Two sphere of the same material have radii 1 m and 4 m and temperature 4000 K and 2000 K respectively. the energy radiated per second by the first sphere is
Greater then by the second
Less than that by the second
Equal in both cases
The information is incomplete to draw and conclusion
4192.A surface at temperature T0 °K receives power P by radiation from a small sphere at temperature T >> T0 and at a distance d. if both T and d are doubled, the power received by surface will becomes approximately
P
2 P
4 P
16 P
4193.If temperature of a black body increases from 7°C to 287°C, then the rate of energy radiation becomes
5 times
16 times
4 times
2 times
4194.A bucket full of hot water is kept in a room and it cools from 75°C to 70°C in t1 minutes from 70°C to 65°C in t2 minutes and from 65°C to 60°C in t3 minutes; then
t1 - t2 = t3
t1 < t2 < t3
t1 > t2 > t3
t1 < t2 > t3
4195.A body cools from 60°C to 50°C in 10 minutes. If the room temperature is 25°C and assuming Newton’s law of cooling to hold good, the temperature of the body at the end of the next 10 minutes will be
38.5°C
40°C
42.85°C
45°C
4196.Two spheres made of same material have radii in the ratio 2:1. if both the spheres are at same temperature, then what is the ratio of heat radiation energy emitted per second by them
1: 4
4: 1
3: 4
4: 3
4197.Solar radiation emitted by sun resembles that emitted by a black body at a temperature of 6000 K. maximum intensity is emitted at a wavelength of about 4800 A°. if the sun were cooled down from 6000 K to 3000 K, then the peak intensity would occur at a wavelength of
4800 A°
9600 A°
2400 A°
19200 A°
4198.A person with dark skin as compared to a person with white skin will experience
Less heat and less cold
More heat and more cold
More heat and less cold
Less heat and more col
11593.Unit of distance used in navigation is
Nautical mile
Kilometre
Light year
Yard
11594.Match the columns:
List I List II
Forms Quantities
A. Cu sec 1. Pressure
B. Byte 2. Intensity of earthquakes
C. Richter 3. Rate of flow
D. Bar 4. Computer memory
4 1 2 3
2 4 3 1
3 4 2 1
3 2 1 4
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