Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE...
Transcript of Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE...
![Page 1: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/1.jpg)
PHYSICSNEET and JEE Main 2020 : 45 Days Crash Course
Problem Solving Class(Electrostatics, Gravitation and Radiation)
By,Ritesh Agarwal, B. Tech. IIT Bombay
![Page 2: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/2.jpg)
P-Q1416
![Page 3: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/3.jpg)
P-Q1416-Solution
Ans [D]
Fe = ������ ������
When dielectric insert it reduce the force by dielectric constant time �� = �4
![Page 4: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/4.jpg)
P-Q1418
Two similar spheres having +� and −� charge are kept at a certain distance. � force
acts between the two. If in the middle of two spheres, another similar sphere having +� charge is kept, then it experience a force in magnitude and direction as
(a) Zero having no direction (b) 8F towards + � charge
(c) 8F towards − � charge (d) 4F towards + � charge
![Page 5: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/5.jpg)
P-Q1418-Solution
Force formula btw two charge
Direction of force from + to –ve
Ans [C]
![Page 6: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/6.jpg)
P-Q1419
![Page 7: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/7.jpg)
P-Q1419-Solution
For maximum force
�� − 2���� = 0Solving the equation
Force btw 2 chargeAns [A]
![Page 8: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/8.jpg)
P-Q1420
![Page 9: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/9.jpg)
P-Q1420-Solution
2
1
2
2
1
2
1
÷÷ø
öççè
æ=Þ
µ
rr
FF
rF
NF
F
25.11
06.004.05
2
2
2
==
÷øö
çèæ=
Force is inversely proportional to ��
Both moving 0.01m so new distance btw then is 0.04
Ans [B]
![Page 10: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/10.jpg)
P-Q1421
![Page 11: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/11.jpg)
P-Q1421-Solution
Ans [B]
Force formula btw 2 charge
Electrostatic force is vector Quantity so apply vector sum
![Page 12: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/12.jpg)
P-Q1422
![Page 13: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/13.jpg)
P-Q1422-Solution
Charge distribution on surfaces
Net charge on each surface
Ans [A]
![Page 14: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/14.jpg)
P-Q1426
A) 2.36 × 10�� B) 4.72 × 10�� C) 2.16 × 10�� D) 1.23 × 10��
![Page 15: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/15.jpg)
P-Q1426-Solution
Gravitational force
Electrostatic force btw charges
Ans [A]
![Page 16: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/16.jpg)
P-Q1427
A charge q is placed at the Centre of the line joining two equal charges Q. The system
of the three charges will be in equilibrium, if q is equal to
![Page 17: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/17.jpg)
P-Q1427-Solution
Ans [B]Suppose in the following figure, equilibrium of charge B is considered
At equilibrium net force is zero
![Page 18: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/18.jpg)
P-Q1428
![Page 19: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/19.jpg)
P-Q1428-Solution
Relation btw Electric potential and electric field
Ans [A]
![Page 20: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/20.jpg)
P-Q1429
![Page 21: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/21.jpg)
P-Q1429-Solution
Since potential inside the hollow sphere is same as that on the surface.
Ans [B]
Potential inside is 10V
![Page 22: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/22.jpg)
P-Q1430
![Page 23: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/23.jpg)
P-Q1430-Solution
Ans [D]On the equipotential surface, electric field is normal to the charged
surface (where potential exists) so that no work will be done.
Equipotential Surface à same potential across surface
![Page 24: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/24.jpg)
P-Q1431
![Page 25: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/25.jpg)
P-Q1431-Solution
Electric lines force due to negative charge are radially inward.
Field lines come toward negative charge
Ans [C]
![Page 26: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/26.jpg)
P-Q1432
![Page 27: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/27.jpg)
P-Q1432-Solution
Potential due to all four charges Ans [B]
4
![Page 28: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/28.jpg)
P-Q1433
![Page 29: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/29.jpg)
P-Q1433-Solution
In non-uniform electric field. Intensity is more, where the
lines are more denser
More the lines à charge moreMore denser à electric field
Ans [A]
![Page 30: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/30.jpg)
P-Q1434
![Page 31: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/31.jpg)
P-Q1434-Solution
29
20
1094
1rq
rq
E ´´=´=pe
39
26
9
2
100833.2109
)5.2(103109
-´=´
´´=
´´
=rE
q
q should be less than 2.0833 ´ 10–3. In the given set of options 2 ´ 10–3
is the maximum charge which is smaller than 2.0833 ´ 10–3.
Electric field due to charge at distance r
Ans [B]
![Page 32: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/32.jpg)
P-Q1436
![Page 33: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/33.jpg)
P-Q1436-Solution
Ans [D]
Remember this formula
Charge distribute depends on radius
![Page 34: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/34.jpg)
P-Q940
If a body is released from a great distance from the centre of the earth find the velocity
when it strikes the surface of the earth . Take R=6400km
(A)7.2km/s (B)11.8km/s(C) 7.8km/� (D) 11.2km/s
![Page 35: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/35.jpg)
P-Q940-Solution
Ans [D]
It will collide the earth with escape velocity or 11.2km/s
Above result can also be found by taking initial Total energy zero.
Energy conservation 0 = 12��� − ���� Energy on the surface of earth, when body hits
�� = 2���� = 2��� Putting the value of all constants
= 11.2��/�
![Page 36: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/36.jpg)
P-Q943
(A)
(C)
(B)
(D)
![Page 37: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/37.jpg)
P-Q943-Solution
Ans [C]
Centripetal force is provided by the gravitational force of attraction between two particles
![Page 38: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/38.jpg)
P-Q944
(A)
(C)
(B)
(D)
![Page 39: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/39.jpg)
P-Q944-Solution
Ans [D]
Earth revolving around sun so there is centripetal force
![Page 40: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/40.jpg)
P-Q947
(A)
(C)
(B)
(D)
![Page 41: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/41.jpg)
P-Q947-Solution
Ans [B]
Variation of g with height and
depth respectively
![Page 42: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/42.jpg)
P-Q949
(A)
(C)
(B)
(D)
![Page 43: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/43.jpg)
P-Q949-Solution
Ans [B]
Gravitation on planet
Gravitation on Earth
![Page 44: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/44.jpg)
P-Q952
(A)
(C)
(B)
(D)
![Page 45: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/45.jpg)
P-Q952-Solution
Ans [B]
Gravitation varies with depth like this
Gravitation decreases as we go depth
![Page 46: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/46.jpg)
P-Q954
(A)
(C)
(B)
(D)
![Page 47: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/47.jpg)
P-Q954-Solution
Ans [B]
Given that gravity is only 25% of that on earth
![Page 48: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/48.jpg)
P-Q958
(A)
(C)
(B)
(D)
![Page 49: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/49.jpg)
P-Q958-Solution
Ans [B]
So the weight of the body at this height will become one fourth.
![Page 50: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/50.jpg)
P-Q2635
We consider the radiation emitted by the human body. Which of the following statements
is true
(A) The radiation is emitted only during the day
(B) The radiation is emitted during the summers and absorbed during the winters
(C) The radiation emitted lies in the ultraviolet region and hence is not visible
(D) The radiation emitted is in the infra-red region
![Page 51: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/51.jpg)
P-Q2635-Solution
Ans [D]The radiation emitted by the human body is in the infra-red region.
Every body at all time, at all temperatures emits radiation (except at T = 0 K)
T = 0 K is known as absolute zero temperature
![Page 52: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/52.jpg)
P-Q2636
Good absorbers of heat are :
(A) Poor emitters (B) Non-emitters
(C) Good emitters (D) Highly polished
![Page 53: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/53.jpg)
P-Q2636-Solution
Ans [C]Good absorbers are always good emitters of heat
Sand is a good absorber of heat but also good emitter of heat that is why Days are hotter
and nights are colder in deserts as compare to the other places
![Page 54: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/54.jpg)
P-Q2656
Liquid is filled in a vessel which is kept in a room with temperature 20°C . When the
temperature of the liquid is 80°C, then it loses heat at the rate of 60 cal/sec. . What will
be the rate of loss of heat when the temperature of the liquid is 40°C.
(A) 180 cal/sec (B) 40 cal/sec
(C) 30 cal/sec (D) 20 cal/sec
![Page 55: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/55.jpg)
P-Q2656-Solution
Ans [D]
Rate of loss of heat ∆�� temperature difference Dq
![Page 56: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/56.jpg)
P-Q2658
A body takes 5 minute to cool from 80°C to 50°C. How much time it will take to cool from 60°C
to 30°C, if room temperature is 20°C.
(A) 40 minute (B) 9 minute
(C) 30 minute (D) 20 minute
![Page 57: Physics Problem Solving Electrostatics, Gravitation and ......2020/06/15 · PHYSICS NEET and JEE Main 2020 : 45 Days Crash Course Problem Solving Class (Electrostatics, Gravitation](https://reader036.fdocuments.net/reader036/viewer/2022090811/611cef0b556a5225d92746e5/html5/thumbnails/57.jpg)
P-Q2658-Solution
Ans [B]
Dividing equation (i) by (ii) we
get
According to Newton’s law of cooling.