Practice problems on NEET, NEET 2014

Question 1

If force (F) , velocity (V)  and time (T)  are taken as fundamental units, then the dimensions of mass are:

Accepted Answer

[FV−1T]

Answer

[FVT−1]

Answer

[FVT−2]

Answer

[FV−1T−1]

Question 2

A projectile is fired from the surface of the earth with a velocity of 5 ms−1  and angle θ  with the horizontal. Another projectile fired from another planet with a velocity of 3 ms−1  at the same angle follows a trajectory which is identical with the trajectory of the projectile fired from the earth. The value of the acceleration due to gravity on the planet is (  in ms−2)  given g=9.8 m/s2.

Accepted Answer

3.5

Answer

5.9

Answer

16.3

Answer

110.8

Question 3

A particle is moving such that its position coordinate (x, y) are (2m,3m) at time t=0 (6m,7m) at time t=2s and (13m,14m) at time t=5 s.Average velocity vector (Vav​)  from t=0  to t=5s is :

Accepted Answer

511​(i^+j^​)

Answer

51​(13i^+14j^​)

Answer

37​(i^+j^​)

Answer

2(i^+j^​)

Question 4

A system consists of three masses m1​,m2​ and m3​  connected by a string passing over a pulley P. The mass m1​  hangs freely and m2​  and m3​ are on a rough horizontal table (the coefficient of friction =mu  ). The pulley is frictionless and of negligible mass. The downward acceleration of mass m1​  is:(Assume m1​=m2​=m3​=m  )

Accepted Answer

3g(1−2μ)​

Answer

9g(1−gμ)​

Answer

32gμ​

Answer

2g(1−2μ)​

Question 5

If the sum of all external forces acting on a system is zero, then

Accepted Answer

Momentum of the system is constant

Answer

Particles inside the  system must be rest

Answer

System has no velocity

Answer

None of these

Question 6

A balloon with mass ' m  ' is descending down with an acceleration 'a' (where a<g  ). How much mass should be removed from it so that it starts moving up with an acceleration 'a' ?

Accepted Answer

g+a2ma​

Answer

g−a2ma​

Answer

g+ama​

Answer

g−ama​

Question 7

A body of mass (4 m) is lying in x−y  plane at rest. It suddenly explodes into three pieces. Two pieces, each of mass (m)  move perpendicular to each other with equal speeds (v). The total kinetic energy generated due to explosion is :

Accepted Answer

23​mv2

Answer

mv2

Answer

2mv2

Answer

4mv2

Question 8

A solid cylinder of mass 50 kg  and radius 0.5 m  is free to rotate about the horizontal axis. A massless string is wound round the cylinder with one end attached to it and other hanging freely. Tension in the string required to produce an angular acceleration of 2 revolutions s−2  is :

Accepted Answer

157 N

Answer

25 N

Answer

50 N

Answer

78.5 N

Question 9

The ratio of the accelerations for a solid sphere (mass ' m  ' and radius 'R) rolling down an incline of angle ' θ  ' without slipping and slipping down the incline without rolling is :

Accepted Answer

5:7

Answer

2:3

Answer

2:5

Answer

7:5

Question 10

A black hole is an object whose gravitational field is so strong that even light cannot escape from it. To what approximate radius would earth (mass = 5.98×1024 kg  ) have to be compressed to be a black hole?

Accepted Answer

10−2 m

Answer

10−9 m

Answer

10−6 m

Answer

100 m

Question 11

Copper of fixed volume V ; is drawn into wire of length ' l  When this wire is subjected to a constant force ' F  ', the extension produced in the wire is ' Δl . Which of the following graphs is a straight line ?

Accepted Answer

Δl versus R

Answer

Δl  versus l1​

Answer

Λl versus p1​

Answer

Al versus l

Question 12

A certain number of spherical drops of a liquid of radius ' r  ' coalesce to form a single drop of radius ' R  ' and volume V . If ' T  is the surface tension of the liquid, then :

Accepted Answer

energy =3VT(r1​−R1​)  is released

Answer

energy =4VT(r1​−R1​) is released

Answer

energy =3VT(r1​+R1​)  is absorbed

Answer

Energy is neither released nor absorbed

Question 13

Steam at 100∘C  is passed into 20 g  of water at 10∘C . When water acquires a temperature of 80∘C , the mass of water present will be:[Take specific heat of water=1calg−1∘C−1  and latent heat of steam =540calg−1]

Accepted Answer

22.5 g

Answer

24 g

Answer

31.5 g

Answer

42.5 g

Question 14

Certain quantity of water cools from 70∘ to 60∘  in the first 5 minutes and to 54∘C  in the next 5 minutes. The temperature of the surroundings is:

Accepted Answer

45∘C

Answer

20∘C

Answer

42∘C

Answer

10∘C

Question 15

A monoatomic gas at a pressure P,  having a volume V  expands isothermally to a volume 2 V  and then adibatically to a volume 16 V.  The final pressure of the gas is : (take γ=35​ )

Accepted Answer

64P​

Answer

64P

Answer

32P

Answer

16P

Question 16

A thermodynamic system undergoes cyclic process mathrmABCDA  as shown in fig. The work done by the system in the cycle is :

Accepted Answer

Zero

Answer

P0​ V0​

Answer

2P0​ V0​

Answer

2P0​ V0​​

Question 17

The mean free path of molecules of a gas, (radius ' r  ') is inversely proportional to :

Accepted Answer

r2

Answer

r3

Answer

r

Answer

r​

Question 18

If n1​,n2​ and n3​ are the fundamental frequencies of three segments into which a string is divided, then the original fundamental frequency n of the string is given by :

Accepted Answer

n1​=n1​1​+n2​1​+n3​1​

Answer

n​1​=n1​​1​+n2​​1​+n3​​1​

Answer

n​=n1​​+n2​​+n3​​

Answer

n=n1​+n2​+n3​