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Practice each question, then open the answer or worked solution.
Young’s modulus of steel is 1.9 × 1011 N/m2. When expressed in CGS units of dynes/cm2, it will be equal to:
a) 1.9 × 1010
b) 1.9 × 1011
c) 1.9 × 1012
d) 1.9 × 1013
The correct answer is c) 1.9 × 1012
If momentum (P), area (A), and time (T) are taken to be fundamental quantities, then energy has the dimensional formula
a) (P1A-1T1)
b) (P2A1T1)
c) (P1A-1/2T1)
d) (P1A1/2T-1)
The correct answer is d) (P1A1/2T-1)
Multiple Choice Questions IIOn the basis of dimensions, decide which of the following relations for the displacement of a particle undergoing simple harmonic motion is not correct:
The correct answer is b) y = a sin vt and c) y = a/T sin (t/a)
If P, Q, and R are physical quantities having different dimensions, which of the following combinations can never be a meaningful quantity?
e) (R + Q)/P
The correct answer is d) (PR – Q2)/R and e) (R + Q)/P
Photon is quantum of radiation with energy E = hv where v is frequency and h is Planck’s constant. The dimensions of h are the same as that of:
a) linear impulse
b) angular impulse
c) linear momentum
d) angular momentum
The correct option is b) angular impulse and d) angular momentum
If Planck’s constant (h) and speed of light in vacuum (c) are taken as two fundamental quantities, which of the following can also be taken to express length, mass, and time in terms of the three chosen fundamental quantities?
The correct answer is a) mass of electron b) universal gravitational constant and d) mass of proton
Which of the following ratios express pressure?
The correct answer is a) force/area and b) energy/volume
Which of the following are not a unit of time?
The correct answer is b) parsec and d) light year
Very Short AnswersWhy do we have different units for the same physical quantity?
We have different units for the same physical quantity because they differ from place to place.
The radius of an atom is of the order of 1 Å, and radius of nucleus is of the order of fermi. How many magnitudes higher is the volume of the atom as compared to the volume of the nucleus?
Radius of atom = 1 Å = 10-10 m
Radius of nucleus = 1 fermi = 10-15 m
Volume of atom = 4/3πRa3
Volume of nucleus = 4/3πRn3
Vatom/Vnucleus = 1015
Mass of one mole of carbon atom = 12 g = 1.67 × 10-27 kg