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Physics NEET MCQ
Quiz 5
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Q.1
If unit of length, mass and force are chosen as fundamental units, the dimensions of time would be
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a) M1/2L-1/2F1/2
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b) M1/2L1/2F1/2
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c) M1/2 L1/2F-1/2
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d) M L-1/2F-1/2
Explanation
Let dimension of T in terms of M,L,T, be [T] = Ma Lb Fc Dimension of F in terms of MLT is [F] = MLT-2 Thus [M0L0T1] = Ma Lb [MLT-2]c [M0L0T1] = Ma+c Lb+cT-2c Comparing indices we get a+c=0 b+c =0 -2c=1 On solving above equations a = 1/2, b=1/2, c=-1/2, Thus dimensional formula for T in M,L,F is [T] = M1/2 L1/2F-1/2 Answer: (c)
Q.2
Dimensions of L / (RCV) are .. [ Roorkee, 1994]
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a) A-1
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b) A-2
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c) A
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d) A2
Explanation
Dimension of L = [ ML2T-2A-2] Dimension of R = [ML2T-3A-2] Dimension of C = [ M-1L-2T4 A2] Dimension of Potential V = ML2T-3A-1] On substituting and solving we get A-1 Answer: (a)
Q.3
Which of the following has the dimension of pressure? [C.P.M.T 1994]
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a) ML/ T2
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b) M/ (L2T2)
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c) M / LT2
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d) M/LT
Explanation
P=F/A = MLT-2 / L2 P = M/ LT2 Answer:(c)
Q.4
In an experiment to measure the height of a bridge b dropping stone into water underneath, if error in measurement of time is 0.1s at the end of 2s, then the error in estimation of height of bridge will be [ kerala P.E.T. 2004]
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a) 0.49m
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b) 0.98m
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c) 1.96m
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d) 2.12m
Explanation
From s = ut + ½ a t2 h = 0 + ½ × (9.8) (2)2 h = 19.6 m As g is constant Now Δh /h = ± (Δt/t) Δh /h = ± 2(0.1/2) = ± 0.1 Δh = ±h(0.1) Δh = ±19.6×0.1 = 1.96m Answer: (c)
Q.5
Two quantities A and B have different dimensions. Which mathematical operation may be physically meaningful [ C.P.M.T. 1998]
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a) A/B
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b) A+B
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c) A-B
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d) A=B
Explanation
Quantities having different dimensions can't be added or subtracted and also they can't be equal. Answer: (a)
Q.6
When a copper sphere is heated, maximum percentage change will be observed in.. [ AFMC 2003]
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a) radius
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b) area
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c) volume
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d) none of these
Explanation
As volume V ∝ r3 ΔV / V = 3Δr / r Hence maximum percentage change will be observed in volume Answer: (c)
Q.7
If L = 2.251 cm, B = 2.1 cm, then with reference to significant digit L+B = ....
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a)4.351
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b) 4.35
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c) 4.4
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d) 4 cm
Explanation
Smalles t significant figure is 2. Round off as previous figure of 5 is odd, thus increased by 1 Answer : (c)
Q.8
The ratio of the dimension of Planks constant and that of moment of inertia is the dimension of [ C.B.S.E. PMT 2005]
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a) velocity
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b) angular momentum
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c) time
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d) frequency
Explanation
h = E/f Dimensional formula = ML2T2 / T-1 h = ML2T-1 Moment of inertia I = ML2 By taking ratio of dimensional formula of h and I we get h/I = T-1= frequency Answer:(d)
Q.9
A physical quantity A is related to four observables a,b,c,d as follows the percentage of error of measurement is a,b,c,d are 1, 3, 2 and 2 respectively. What is the percentage error in A? [ kerala C.E.T 2005]
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a) 12%
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b) 7%
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c) 14%
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d) 16%
Explanation
Percentage error in A = 14% Answer: (c)
Q.10
The dimensional formula of magnetic flux is .. [ CBSE-PMT 1999]
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a) [ML2T-2A-1]
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b) [ML0T-2A-2]
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c) [M0L-2T-2A-2]
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d) [ML2T-1A3]
Explanation
We know that F = BIl Thus B = F/Il Dimension of B = [ MLT-2 / AL ] B = ML0T-2A-1 Now magnetic flux φ = (B) (area) By substituting dimensions in above formula we get ∴ dimension of φ = ML2T-2A-1] Answer: (a)
Q.11
Length cannot be measured in [ AIIMS 2002]
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a) fermi
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b) micron
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c) debye
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d) light year
Explanation
Answer: (c)
Q.12
Dimensional formula for electrical resistance is [ AIIMS 2005]
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a) ML2T-3A-1
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b) ML2T-3A-2
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c) ML2T3A-2
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d) ML-1T3A2
Explanation
R = V/I Dimensional formula of V = W/Q = [ML2T-2] / AT V = [ML2T-3 A-1] By substituting and solving we we get Dimension formula R = ML2T-3A-2 Answer:(b)
Q.13
Which of the following systems of units is not based on the units of mass, length and time alone? [ keral P.M.T 2004]
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a) S.I.
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b) MKS
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c) FPS
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d) CGS
Explanation
Answer: (a)
Q.14
Chronometer is used to measure [ A.F.M.C 2003]
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a) time
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b) mass
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c) density
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d) distance
Explanation
Answer: (a)
Q.15
Si unit of magnetic dipole moment is [ MPPMT 2002]
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a) Am-1
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b) A m2
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c) T mA-1
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d) mA-2
Explanation
Answer: (b)
Q.16
In the standard equation Sn = u +(a/2)[2n-1], what dimension do you view for Sn?
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a) M0L1T0
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b) M0L-1T1
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c) M0L1T-1
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d) M0L0T1
Explanation
Since equation is dimensionally correct Dimension of Sn must have dimension of velocity Answer:(c)
Q.17
The length of rod a rod is (11.05±0.05)cm. What is the total length of 2 such rods?
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a) (22.1 ±0.05)cm
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b) (22.10±0.05)cm
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c) (22.10±0.05)cm
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d) (22.10±0.10)cm
Explanation
Z±ΔZ = (A+B) ±(ΔA+ΔB) Significant numbers in reading is four thus option (d) is correct Answer: (d)
Q.18
A unit less quantity
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a) may have a non-zero dimension
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b) always have a non-zero dimension
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c) never has a non-zero dimension
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d) does not exist
Explanation
Unit less quantity don't have dimensions Answer: (c)
Q.19
The length and breadth of metal sheet are 3.124m and 3.002m respectively. The area of this sheet up to four correct significant figure is [ AIIMS 2001]
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a) 9.37 m2
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b) 9.378m2
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c) 9.3782 m2
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d) 9.378248 m2
Explanation
Area = 3.124 × 3.002 = 9.378248 m2 area of this sheet up to four correct significant figure is = 9.378 m2 Answer: (b)
Q.20
Out of following pairs, which does not have identical dimensions [ AIEE 2005]
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a) Work and torque
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b) moment of inertia and moment of a force
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c) impulase and momentum
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d) anular moment and plank's constant
Explanation
Moment of Inertia = [ML2] Moment of force = f ×s = [MLT-2] [ L] Moment of force = [ML2T-2] Answer:(b)
Q.21
Power P is related to distance x and time t as The dimensional formula of b is
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a) [M0LT-2
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b) [M0L2T2
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c) [M0L2T-2
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d) [M0L2T0
Explanation
As x subtracted from b, therefore, dimensional formula of b = x2 dimensional formula of b = L2 = [ M0L2T0 Answer: (d)
Q.22
Subtract 2.6×104 from 3.9×105 with due regards to significant figures
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a) 3.64×105
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b) 3.7×105
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c) 3.6 ×105
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d) 3.65 ×106
Explanation
2.6 ×104 = 0.26 ×105 3.9 ×105 - 0.26 ×105 = 3.64×105 Correct up to one place of decimal = 3.6×105 Answer: (c)
Q.23
pressure depends on distance as Where α, β are constant, z is distance, k is Boltzman's constant and θ is temperature. the dimension of β are [ IIT 2004]
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a) M0L0T0
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b) M-1L-1T-1
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c) M0L2T0
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d) M1L1T2
Explanation
Exponential quantity is dimension less let it be C From given equation P = α / β P = kθC / βz --(1) According to equation of Indeal gas for one mole PV = Rθ R/ NA =k PV = kθNA P = kθNA / V --(2) Note that NA is dimentionless constant from equation 1 and 2 we get V is volume dimension L3, z is distance dimension L , and C is dimension less Thus dimension of β = L2 Answer:(c)
Q.24
Which of the following is the dimensional formula for the energy per unit area per second
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a) [ ML0T0]
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b) [ ML0T-3]
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c) [ ML2T-1]
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d) [ ML0T1]
Explanation
Energy / Area-second = [ML2T-2] / ([L2] × [T] ) = ML0T-3 Answer: (b)
Q.25
If p is radiation pressure, C represents speed of light and Q represents radiation energy striking unit area per sond, then non zero integers x, y, and z such that PxQyCz is dimensionless are [CPMT 1992]
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a) x=1, y =1, z=-1
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b) x=1, y = -1, z=1
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c) x=-1, y=1, z=1
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d) x=1, y=1,z=1
Explanation
Given PxQyCz =[M0L0T0] ∴ From above x+y = 0 -x+z = 0 -2x-3y-z = 0 On solving above equations we get x = 1, y =-1, z= 1 Answer: (b)
Q.26
A pressure of 106 dyne/cm2 is equivalent to ..
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a) 105 N / m²
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b) 104 N / m²
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c) 106 N / m²
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d) 107 N / m²
Explanation
Now Dimension of pressure is [ ML-1T-2 ∴ a = 1, b=-1, c=-2 Given that n2 = 106 dyne/cm2 Answer: (a)
Q.27
the mass of a beaker is found to be (10.1±0.1) gm when empty and (17.3±0.1)gm when partially filled with a liquid. What is the best value for the mass of the liquid together with the possible limits of accuracy
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a) (7.2±0.2)gm
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b) (7.2±0.1)gm
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c) (7.1±0.2)gm
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d) (7.2±0.3)gm
Explanation
mass of liquid = Mass of beaker filled with liquid - Mass of empty beaker mass of liquid = (17.3±0.1) - (10.1±0.1) = 7.2±0.2 Note error are always added while subtracting or adding Answer:(a)
Q.28
Equation for the state of a gas is where a, b, c and R are constants. the isothermal can be represented by P = AVm - BVn where A and B depends only on temperature and .. [CBSE1995]
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a) m = - and n=-1
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b) m =c and n= 1
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c) m =-c and n=1
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d) m = c and n = -1
Explanation
Dividing equation by by Vc and adjusting terms we get Now P = AVm - BVn --(2) comparing above two equations we get m --c and n = -1 Answer: (a)
Q.29
If Force(F), Area(A) and density(D) are taken as the fundamental units, the representation of Young's Modulus will be
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a) F-1A-1D-1
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b) FA-2D2
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c) FA-1D0
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d) FA-1D
Explanation
Let Y = [ Fa Ab Dc] Dimensional formula of Young's modulus = [ML-1T-2 ] Thus [ML-1T-2 ]= [ MLT-2]a[L2]b[ML-3]c [ML-1T-2 ] = [ Ma+c La+2b-3c T-2a-3c By comparing a+c = 1 a+2b-3c = -1 -2a-2c = -2 on solving c= 0, a = 1, b= -1 Answer: (c)
Q.30
The dimensions of physical quantity X in the equation Force= X/(density) is given by
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a) ML4T-2
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b) M2L-2T-1
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c) M2L-2T-2
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d) ML-2T-1
Explanation
Form given equation X = F˜(Density) Dimension of X = [MLT-2][ML-3] Dimension of X = [M2L-2T-2 Answer: (c)
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