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Physics 4 Marks Questions

Circular Motion · Rajasthan Board (RBSE) STD 12 Science (Rajasthan - English Medium). 5 questions.

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4 Marks Questions

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5 questions · self-marked practice — reveal the answer and mark yourself.

Question 14 Marks
After a good meal at a party you wash your hands and find that you have forgotten to bring your handkerchief. You shake your hands vigorously to remove the water as much as you can. Why is water removed in this process?
Answer
As you move your hands in circular motion the water due to centrifugal force drags away from your hand as you shake your hands vigorously the frictional force between your and and water becomes comparably low.
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Question 24 Marks
Some washing machines have cloth driers. It contains a drum in which wet clothes are kept. As the drum rotates, the water particles get separated from the cloth. The general description of this action is that "the centrifugal force throws the water particles away from the drum". Comment on this statement from the viewpoint of an observer rotating with the drum and the observer who is washing the clothes.
Answer
The observer inside drum would feel centrifugal force and thus it will stick to the wall of drum while the observer will feel it self on rest and the water inside cloths would rinse from it and pass through small holes on the walls of drum due to centrifugal force. and as seen by observer who is washing the cloths, cloths are rotating at high speed while sticking to the sides of drum.
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Question 34 Marks
A small coin is placed on a record rotating at $33\frac{1}{3}$ rev/ minute. The coin does not slip on the record. Where does it get the required centripetal force from?
Answer
The frictional force between coin and record would not let the coin slip away from the record as the record is at low revolution speed thus frictional force is grater than centrifugal force.
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Question 44 Marks
A car driver going at some speed v suddenly finds a wide wall at a distance r. Should he apply brakes or turn the car in a circle of radius r to avoid hitting the wall?
Answer
Driver can go for both options. But to avoid from colliding car from wide wall the car needs to take a u-turn. So we may prefer applying brakes than turning car around.
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Question 54 Marks
A bird while flying takes a left turn, where does it get the centripetal force from?
Answer
The centripetal wings of bird w.r.t to air and thus the bird turns toward left.
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