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- Question
What is refractive index ?
Options- A. it is defined as the ratio of speed of light in the medium to the speed of light in vacuum.
- B. it is defined as the product of speed of light in medium and in vacuum.
- C. it is defined as the ratio of speed of light in vacuum to the speed of light in the medium .
- D. None of above
- Correct Answer
- it is defined as the ratio of speed of light in vacuum to the speed of light in the medium .
- 1. In case of uniform circular motion, the acceleration is
Options- A. Variable in magnitude but constant in direction
- B. Constant in magnitude and directed radially inwards
- C. Variable in magnitude but tangential to the circle
- D. Zero Discuss
- 2. A boy is swinging a ball attached to a string in a horizontal 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
- 3. In the case of bodies falling under gravity which of the following remains constant at a given place?
Options- A. Kinetic energy
- B. Potential energy
- C. acceleration
- D. all the above Discuss
- 4. A boy sitting in a train moving with a uniform velocity drops a coin outside. A man standing outside the train will find the trajectory of the coin to be
Options- A. a parabola
- B. a horizontal straight line
- C. a vertical straight line
- D. a circle Discuss
- 5. When one enters a dark room after being in bright light one is not able to see anything clearly for a while because
Options- A. the retina of the eye moves forward
- B. the retina of the eye moves backward
- C. the iris is unable to dilate the pupil immediately to be able to see things
- D. the eye has no power of accommodation Discuss
- 6. 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
- 7. 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
- 8. 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
- 9. 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
- 10. 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
Physics problems
Search Results
Correct Answer: Variable in magnitude but constant in direction
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. (B) is Correct.
Correct Answer: acceleration
Explanation:
This acceleeration denoted by letter g varies from place to place. Unless stated otherwise, it can be taken 9.8 m/ .
Correct Answer: a parabola
Explanation:
Parabola, because when the coin is dropped at a particular point, it has the same velocity as the running train. So, by Newton's first law, it continues its motion horizontally with that velocity. But then, it is also pulled down by earth's gravity continuously. In this situation its horizontal motion gives way to the parabolic motion until it reaches the ground.
Correct Answer: the iris is unable to dilate the pupil immediately to be able to see things
Explanation:
The size of the pupil of the automatically adjusts itself according to the intensity of light passing through it; if the intensity is more, the size is less, if less, it is more. So in our case the pupil should dilate i.e , increase in size to be able to see in the dark. This switchover takes some time. But here the entry into the dark room is immediate. So the eye has no time to adjust itself and hence is not able to see at all for a while.
Correct Answer: at a higher alevation than the bird
Explanation:
The trajectory of the bullet is a parabola
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: 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: 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: 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.
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