NEET 2021 Past Year Paper with Detailed Solutions | NEET Past Year Papers PDF Download

 Page 1


 
 
 
PHYSICS 
 
1. An infinitely long straight conductor carries a current of 5?? as shown. An electron is moving with a speed of 10
5
m/s 
parallel to the conductor. The perpendicular distance between the electron and the conductor is 20cm at an instant. 
Calculate the magnitude of the force experienced by the electron at that instant. 
 
(1) 4× 10
-20
N 
(2) 8?? × 10
-20
N 
(3) 4?? × 10
-20
N 
(4) 8× 10
-20
N 
Correct Answer: (4) 
Q.1. Solution: 
M.F due to long current carrying wire at 20 cm , 
?? =
?? 0
?? 2????
 
?? =
2× 10
-7
× 5
20× 10
-2
 
?? = 0.5 × 10
-5
 T 
Now, 
Force experienced by electron = ?? V?? 
?? ?? = ?????? 
Page 2


 
 
 
PHYSICS 
 
1. An infinitely long straight conductor carries a current of 5?? as shown. An electron is moving with a speed of 10
5
m/s 
parallel to the conductor. The perpendicular distance between the electron and the conductor is 20cm at an instant. 
Calculate the magnitude of the force experienced by the electron at that instant. 
 
(1) 4× 10
-20
N 
(2) 8?? × 10
-20
N 
(3) 4?? × 10
-20
N 
(4) 8× 10
-20
N 
Correct Answer: (4) 
Q.1. Solution: 
M.F due to long current carrying wire at 20 cm , 
?? =
?? 0
?? 2????
 
?? =
2× 10
-7
× 5
20× 10
-2
 
?? = 0.5 × 10
-5
 T 
Now, 
Force experienced by electron = ?? V?? 
?? ?? = ?????? 
 
 
?? ?? = 1.6× 10
-19
× 10
5
× 0.5 × 10
-5
 
= 8 × 10
-20
 N 
 
2. A body is executing simple harmonic motion with frequency 'n', the frequency of its potential energy is: 
(1) n 
(2) 2?? 
(3) 3n 
(4) 4n 
Correct Answer: (2) 
Q.2. Solution: 
Given, 
frequency of SIHM = ?? 
as we know, 
? In one time period ???? become maximum & minimum two time  
So, 
It means frequency of ????  is 2?? . 
 
3. A radioactive nucleus 
?? A
X undergoes spontaneous decay in the sequence 
Z
A
X ?
Z-1
B ?
Z-3
C ?
Z-2
D where 
 Z  is the atomic number of element X. The possible decay particles in the sequence are: 
(1) ?? ,?? -
,?? +
 
(2) ?? ,?? +
,?? -
 
(3) ?? +
,?? ,?? -
 
(4) ?? -
,?? ,?? +
 
Correct Answer: (3) 
Q.3. Solution: 
As we know due to ?? -decay atomic number decreases by 2 and mass number decreases by 4. Due to ?? -
decay 
mass number remains unchange and atomic number increases by 1. 
Due to  ?? +
 decay mass number remains unchange but atomic number decreares by 1.  
Page 3


 
 
 
PHYSICS 
 
1. An infinitely long straight conductor carries a current of 5?? as shown. An electron is moving with a speed of 10
5
m/s 
parallel to the conductor. The perpendicular distance between the electron and the conductor is 20cm at an instant. 
Calculate the magnitude of the force experienced by the electron at that instant. 
 
(1) 4× 10
-20
N 
(2) 8?? × 10
-20
N 
(3) 4?? × 10
-20
N 
(4) 8× 10
-20
N 
Correct Answer: (4) 
Q.1. Solution: 
M.F due to long current carrying wire at 20 cm , 
?? =
?? 0
?? 2????
 
?? =
2× 10
-7
× 5
20× 10
-2
 
?? = 0.5 × 10
-5
 T 
Now, 
Force experienced by electron = ?? V?? 
?? ?? = ?????? 
 
 
?? ?? = 1.6× 10
-19
× 10
5
× 0.5 × 10
-5
 
= 8 × 10
-20
 N 
 
2. A body is executing simple harmonic motion with frequency 'n', the frequency of its potential energy is: 
(1) n 
(2) 2?? 
(3) 3n 
(4) 4n 
Correct Answer: (2) 
Q.2. Solution: 
Given, 
frequency of SIHM = ?? 
as we know, 
? In one time period ???? become maximum & minimum two time  
So, 
It means frequency of ????  is 2?? . 
 
3. A radioactive nucleus 
?? A
X undergoes spontaneous decay in the sequence 
Z
A
X ?
Z-1
B ?
Z-3
C ?
Z-2
D where 
 Z  is the atomic number of element X. The possible decay particles in the sequence are: 
(1) ?? ,?? -
,?? +
 
(2) ?? ,?? +
,?? -
 
(3) ?? +
,?? ,?? -
 
(4) ?? -
,?? ,?? +
 
Correct Answer: (3) 
Q.3. Solution: 
As we know due to ?? -decay atomic number decreases by 2 and mass number decreases by 4. Due to ?? -
decay 
mass number remains unchange and atomic number increases by 1. 
Due to  ?? +
 decay mass number remains unchange but atomic number decreares by 1.  
 
 
So, option (3) is correct option. 
 
4. The escape velocity from the Earth's surface is ?? . The escape velocity from the surface of another planet having a 
radius, four times that of Earth and same mass density is : 
(1) ?? 
(2) 2?? 
(3) 3?? 
(4) 4?? 
Correct Answer: (4) 
Q.4. Solution: 
As we know escape velocity is given by, 
?? ?? = v2???? =
v
2???? 4
3
?? ?? 3
4
3
?? ?? 2
=
v
2???? ?? 4
3
?? ?? 2
 
?? ?? ?
v
?? 2
? ?? 
Escape velocity from Earth’s surface = ?? 
Escape velocity from surface of another planet =? 
?? ???????????? = 4?? ???????? h
 
?? ???????????? = ?? ???????? h
 
So we can write , 
(?? ?? )
earth 
(?? ?? ) planet 
=
 ?? ???????? h
 
?? ???????????? =
?? 4?? =
1
4
 
It means, 
(?? ?? )
earth 
= (?? ?? )
Planet
 
 
(?? ?? )
Planet
 
= 4?? 
 
Page 4


 
 
 
PHYSICS 
 
1. An infinitely long straight conductor carries a current of 5?? as shown. An electron is moving with a speed of 10
5
m/s 
parallel to the conductor. The perpendicular distance between the electron and the conductor is 20cm at an instant. 
Calculate the magnitude of the force experienced by the electron at that instant. 
 
(1) 4× 10
-20
N 
(2) 8?? × 10
-20
N 
(3) 4?? × 10
-20
N 
(4) 8× 10
-20
N 
Correct Answer: (4) 
Q.1. Solution: 
M.F due to long current carrying wire at 20 cm , 
?? =
?? 0
?? 2????
 
?? =
2× 10
-7
× 5
20× 10
-2
 
?? = 0.5 × 10
-5
 T 
Now, 
Force experienced by electron = ?? V?? 
?? ?? = ?????? 
 
 
?? ?? = 1.6× 10
-19
× 10
5
× 0.5 × 10
-5
 
= 8 × 10
-20
 N 
 
2. A body is executing simple harmonic motion with frequency 'n', the frequency of its potential energy is: 
(1) n 
(2) 2?? 
(3) 3n 
(4) 4n 
Correct Answer: (2) 
Q.2. Solution: 
Given, 
frequency of SIHM = ?? 
as we know, 
? In one time period ???? become maximum & minimum two time  
So, 
It means frequency of ????  is 2?? . 
 
3. A radioactive nucleus 
?? A
X undergoes spontaneous decay in the sequence 
Z
A
X ?
Z-1
B ?
Z-3
C ?
Z-2
D where 
 Z  is the atomic number of element X. The possible decay particles in the sequence are: 
(1) ?? ,?? -
,?? +
 
(2) ?? ,?? +
,?? -
 
(3) ?? +
,?? ,?? -
 
(4) ?? -
,?? ,?? +
 
Correct Answer: (3) 
Q.3. Solution: 
As we know due to ?? -decay atomic number decreases by 2 and mass number decreases by 4. Due to ?? -
decay 
mass number remains unchange and atomic number increases by 1. 
Due to  ?? +
 decay mass number remains unchange but atomic number decreares by 1.  
 
 
So, option (3) is correct option. 
 
4. The escape velocity from the Earth's surface is ?? . The escape velocity from the surface of another planet having a 
radius, four times that of Earth and same mass density is : 
(1) ?? 
(2) 2?? 
(3) 3?? 
(4) 4?? 
Correct Answer: (4) 
Q.4. Solution: 
As we know escape velocity is given by, 
?? ?? = v2???? =
v
2???? 4
3
?? ?? 3
4
3
?? ?? 2
=
v
2???? ?? 4
3
?? ?? 2
 
?? ?? ?
v
?? 2
? ?? 
Escape velocity from Earth’s surface = ?? 
Escape velocity from surface of another planet =? 
?? ???????????? = 4?? ???????? h
 
?? ???????????? = ?? ???????? h
 
So we can write , 
(?? ?? )
earth 
(?? ?? ) planet 
=
 ?? ???????? h
 
?? ???????????? =
?? 4?? =
1
4
 
It means, 
(?? ?? )
earth 
= (?? ?? )
Planet
 
 
(?? ?? )
Planet
 
= 4?? 
 
 
 
5. The half-life of a radioactive nuclide is 100 hours. The fraction of original activity that will remain after 150 hours 
would be : 
(1) 1/2 
(2) 
1
2v2
 
(3) 
2
3
 
(4) 
2
3v2
 
Correct Answer: (2) 
Q.5. Solution: 
Given, 
?? 1
2
= 100 hours 
?? = 150 hours 
? no. of nuclide remain after ?? half life, ?? =
?? 0
2
?? 
? 100 hours = 1 half life 
 150 hours =
1
100
× 150 
=
3
2
 half life 
So, Fraction Remain after 
3
2
 half life 
?? ?? 0
= (
1
2
)
3/2
=
1
2v2
  
 
6. A convex lens 'A' of focal length 20cm and a concave lens ' ?? ' of focal length 5cm are kept along the same axis with a 
distance 'd' between them. If a parallel beam of light falling on 'A' leaves 'B' as a parallel beam, then the distance 'd' in cm 
will be : 
(1) 25 
(2) 15 
(3) 50 
(4) 30 
Page 5


 
 
 
PHYSICS 
 
1. An infinitely long straight conductor carries a current of 5?? as shown. An electron is moving with a speed of 10
5
m/s 
parallel to the conductor. The perpendicular distance between the electron and the conductor is 20cm at an instant. 
Calculate the magnitude of the force experienced by the electron at that instant. 
 
(1) 4× 10
-20
N 
(2) 8?? × 10
-20
N 
(3) 4?? × 10
-20
N 
(4) 8× 10
-20
N 
Correct Answer: (4) 
Q.1. Solution: 
M.F due to long current carrying wire at 20 cm , 
?? =
?? 0
?? 2????
 
?? =
2× 10
-7
× 5
20× 10
-2
 
?? = 0.5 × 10
-5
 T 
Now, 
Force experienced by electron = ?? V?? 
?? ?? = ?????? 
 
 
?? ?? = 1.6× 10
-19
× 10
5
× 0.5 × 10
-5
 
= 8 × 10
-20
 N 
 
2. A body is executing simple harmonic motion with frequency 'n', the frequency of its potential energy is: 
(1) n 
(2) 2?? 
(3) 3n 
(4) 4n 
Correct Answer: (2) 
Q.2. Solution: 
Given, 
frequency of SIHM = ?? 
as we know, 
? In one time period ???? become maximum & minimum two time  
So, 
It means frequency of ????  is 2?? . 
 
3. A radioactive nucleus 
?? A
X undergoes spontaneous decay in the sequence 
Z
A
X ?
Z-1
B ?
Z-3
C ?
Z-2
D where 
 Z  is the atomic number of element X. The possible decay particles in the sequence are: 
(1) ?? ,?? -
,?? +
 
(2) ?? ,?? +
,?? -
 
(3) ?? +
,?? ,?? -
 
(4) ?? -
,?? ,?? +
 
Correct Answer: (3) 
Q.3. Solution: 
As we know due to ?? -decay atomic number decreases by 2 and mass number decreases by 4. Due to ?? -
decay 
mass number remains unchange and atomic number increases by 1. 
Due to  ?? +
 decay mass number remains unchange but atomic number decreares by 1.  
 
 
So, option (3) is correct option. 
 
4. The escape velocity from the Earth's surface is ?? . The escape velocity from the surface of another planet having a 
radius, four times that of Earth and same mass density is : 
(1) ?? 
(2) 2?? 
(3) 3?? 
(4) 4?? 
Correct Answer: (4) 
Q.4. Solution: 
As we know escape velocity is given by, 
?? ?? = v2???? =
v
2???? 4
3
?? ?? 3
4
3
?? ?? 2
=
v
2???? ?? 4
3
?? ?? 2
 
?? ?? ?
v
?? 2
? ?? 
Escape velocity from Earth’s surface = ?? 
Escape velocity from surface of another planet =? 
?? ???????????? = 4?? ???????? h
 
?? ???????????? = ?? ???????? h
 
So we can write , 
(?? ?? )
earth 
(?? ?? ) planet 
=
 ?? ???????? h
 
?? ???????????? =
?? 4?? =
1
4
 
It means, 
(?? ?? )
earth 
= (?? ?? )
Planet
 
 
(?? ?? )
Planet
 
= 4?? 
 
 
 
5. The half-life of a radioactive nuclide is 100 hours. The fraction of original activity that will remain after 150 hours 
would be : 
(1) 1/2 
(2) 
1
2v2
 
(3) 
2
3
 
(4) 
2
3v2
 
Correct Answer: (2) 
Q.5. Solution: 
Given, 
?? 1
2
= 100 hours 
?? = 150 hours 
? no. of nuclide remain after ?? half life, ?? =
?? 0
2
?? 
? 100 hours = 1 half life 
 150 hours =
1
100
× 150 
=
3
2
 half life 
So, Fraction Remain after 
3
2
 half life 
?? ?? 0
= (
1
2
)
3/2
=
1
2v2
  
 
6. A convex lens 'A' of focal length 20cm and a concave lens ' ?? ' of focal length 5cm are kept along the same axis with a 
distance 'd' between them. If a parallel beam of light falling on 'A' leaves 'B' as a parallel beam, then the distance 'd' in cm 
will be : 
(1) 25 
(2) 15 
(3) 50 
(4) 30 
 
 
Correct Answer: (1) 
Q.6. Solution: 
 
Total distance = ?? 1
+ ?? 2
 
= 25 ????  
 
7. A capacitor of capacitance '?? ', is connected across an ac source of voltage ?? , given by V = V
0
sin ?? t The displacement 
current between the plates of the capacitor, would then be given by: 
(1) I
d
= V
0
?? Ccos?? t 
(2) I
d
=
V
0
?? C
cos ?? t 
(3) ?? ?? =
?? 0
????
sin ???? 
 (4) I
d
= V
0
?? Csin ?? t 
Correct Answer: (1) 
Q.7. Solution: 
?  ?? = ????  
And ?? = ?? 0
sin???? 
?? ?? =?  
As we know, 
?  ?? ?? = ?? 0
?? Ø
????
  
= ?? 0
??????
????
    (?  ?? =
?? ?? ) 
=
?? 0
?? ????
?? ????