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- Question
A stone floor feels cold to the bare feet but a carpet on the same floor feels warm. This is because
Options- A. the floor and carpet are at different temperatures
- B. the stone conveys the heat away from the feet more rapidly than the carpet
- C. the carpet is a better conductor of heat than the stone
- D. the human body maintains a constant temperature
- Correct Answer
- the stone conveys the heat away from the feet more rapidly than the carpet
ExplanationBoth the floor and the carpet have the same temperature as both are exposed to the same atmosphere. But the former conducts away the heat from the feet better than the carpet as the latter is a non-conductor. So the feet losing more heat, the floor appears cooler to the feet.
- 1. A cup of hot coffee is placed on a metal table in a room. By which of the following methods does it lose heat?
Options- A. conduction and convection only
- B. conduction and radiation only
- C. convection and radiation only
- D. conduction, convection and radiation Discuss
- 2. A balloon filled with hydrogen will
Options- A. continue going upwards uninterrupted
- B. reach a particular height and remain floating
- C. burst after reaching some height
- D. reach a particular height and start coming down Discuss
- 3. The force that keeps a body in a circular motion called
Options- A. the centripetal force
- B. the centrifugual force
- C. the frictional force
- D. all the above Discuss
- 4. A boy is swinging a ball attached to a string in a horizotal circle. If the string snaps
Options- A. the ball will travel towards the center of the circle and fall down
- B. it will continue to travel along a tangent to the circle at the point the ball was at the time of snapping and finally fall down
- C. it will fall down at the same place where the string breaks
- D. None of these Discuss
- 5. A hunter on the ground wishes to shoot a bird on a tree at a distance with his rifle. He has to point the rifle
Options- A. at the lower alevation than the bird
- B. at a higher alevation than the bird
- C. In the same direction as the bird
- D. vertically upwards Discuss
- 6. When two similar sources vibrate with slightly different frequencies , a regular rise and fall occurs in the loudness of tone. This phenomenon is known as
Options- A. doppler effect
- B. beats
- C. resonance
- D. echo Discuss
- 7. When a ray of light is refracted by a prism such that the angle of deviation is minimum then
Options- A. the angle of emergence is equal to the angle of incidence
- B. the angle of emergence is greater than the angle of incidence
- C. the angle of emergence is smaller than the angle of incidence
- D. the sum of the angle of incidence and the angle of emergence is equal to 90 degrees Discuss
- 8. The capacity of a water heater is measured in
Options- A. Gallons
- B. Liters
- C. Meters
- D. Both A & B Discuss
- 9. What is a Contact Force and explain with an example? Discuss
- 10. RADAR is used for
Options- A. detecting and locating the position of objects such as Aeroplanes
- B. locating submerged submarines
- C. locating geostationary satellites
- D. receiving a signals in a radio receiver Discuss
Physics problems
Search Results
Correct Answer: conduction, convection and radiation
Explanation:
Part of the heat is conducted away by the metal table. Convection currents in air near the surface of the coffee are set up which accounts for some heat loss. Heat is also lost by radiation from the hot coffee to the surroundings. Most of the heat is lost by the last method.
Correct Answer: reach a particular height and remain floating
Explanation:
It will stop at a height where the weight of the balloon with contents is equal to the weight of air displaced by it, i.e , when the upthrust is equal to the downthrust. The question of bursting will depend on how much difference of pressure inside and outside , the material of the balloon can withstand. It is assumed the balloon is filled with a lighter than air gas like hydrogen or helium.
Correct Answer: the centripetal force
Explanation:
without this centripetal force, circular motion is not possible. It acts radially towards the centre and if this force is removed there will be no circular motion but the revolving body will fly off at a tangent.
Correct Answer: it will continue to travel along a tangent to the circle at the point the ball was at the time of snapping and finally fall down
Explanation:
The centripetal force having been removed the body cannot execute the curved path
Correct Answer: at a higher alevation than the bird
Explanation:
The trajectory of the bullet is a parabola
Correct Answer: beats
Explanation:
Beats means the periodic increase and decrease in loudness heard when two notes of nearly the same frequency are sounded simultaneously.
Correct Answer: the angle of emergence is equal to the angle of incidence
Correct Answer: Both A & B
Explanation:
The capacity of a water heater is measured in Gallons or Liters. In the USA, it is measured in Gallons and in India, we measure it in Liters.
Hence, if the capacity of the water heater is 15 gallons or 15 liters, then it says that it can hold 15 gallons or 15 liters of water.
Correct Answer: A Contact force is a force applied to a body by another body that is in contact with it Contact force acts on a point of direct contact between the two objects This force can either be continuous as a continuous force or can be momentary in the form of an impulse Contact force is governed by Newton?s Laws Examples :: Contact force is responsible for most of the interactions we experience in the daily life 1 Writing your name with a pen, pushing a car up a hill, lifting an object, etc 2 Kicking a ball, hammering a nail, etc are some of the everyday examples where contact forces are at work In the first case, the force is continuously applied by the person on the car or pen or an object while in the second case the force is delivered in a short impulse Contact forces are often decomposed into orthogonal components one perpendicular to the surface in contact called the normal force, and one parallel to the surface in contact, called the friction force
Correct Answer: detecting and locating the position of objects such as Aeroplanes
Explanation:
RADAR - RAdio Detection And Ranging.
A radar system consists of a transmitter producing electromagnetic waves in the radio or microwaves domain, a transmitting antenna, a receiving antenna (often the same antenna is used for transmitting and receiving) and a receiver and processor to determine properties of the objects.
Radar is an object-detection system that uses radio waves to determine the range, angle, or velocity of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain.
Radio waves from the transmitter reflect off the object and return to the receiver, giving information about the object's location and speed.
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