1. The gravitational constant is G = 6.67 × 10^−11 m^3 kg^−1 s^−2. Its value in cm^3 g^−1 s^−2 is:
A.
6.67 × 10^−14
B.
6.67 × 10^−5
C.
6.67 × 10^−8
D.
6.67 × 10^−2
Correct Answer:
6.67 × 10^−8
Explanation:
Because 1 m^3 = 10^6 cm^3 and 1 kg = 10^3 g, 1 m^3 kg^−1 = 10^3 cm^3 g^−1. Therefore G = 6.67 × 10^−11 × 10^3 = 6.67 × 10^−8 cm^3 g^−1 s^−2.
2. A pressure of 2.40 × 10^5 Pa is expressed in dyn cm^−2 as:
A.
2.40 × 10^4 dyn cm^−2
B.
2.40 × 10^6 dyn cm^−2
C.
2.40 × 10^7 dyn cm^−2
D.
2.40 × 10^10 dyn cm^−2
Correct Answer:
2.40 × 10^6 dyn cm^−2
Explanation:
Since 1 Pa = 1 N m^−2, 1 N = 10^5 dyn and 1 m^2 = 10^4 cm^2. Thus 1 Pa = 10 dyn cm^−2, giving 2.40 × 10^5 Pa = 2.40 × 10^6 dyn cm^−2.
3. The value of Planck's constant is 6.626 × 10^−34 J s. Its value in erg s is:
A.
6.626 × 10^−27 erg s
B.
6.626 × 10^−41 erg s
C.
6.626 × 10^−34 erg s
D.
6.626 × 10^−20 erg s
Correct Answer:
6.626 × 10^−27 erg s
Explanation:
Since 1 J = 10^7 erg, 6.626 × 10^−34 J s = 6.626 × 10^−34 × 10^7 erg s = 6.626 × 10^−27 erg s.
4. A liquid has dynamic viscosity 0.89 mPa s. Its value in poise is:
A.
8.9 × 10^−4 P
B.
8.9 × 10^−3 P
C.
8.9 × 10^−2 P
D.
8.9 P
Correct Answer:
8.9 × 10^−3 P
Explanation:
Since 1 Pa s = 10 P, 1 mPa s = 10^−3 Pa s = 10^−2 P. Therefore 0.89 mPa s = 0.89 × 10^−2 P = 8.9 × 10^−3 P.
5. A surface tension of 0.072 N m^−1 is equivalent to:
A.
0.72 dyn cm^−1
B.
7.2 dyn cm^−1
C.
72 dyn cm^−1
D.
720 dyn cm^−1
Correct Answer:
72 dyn cm^−1
Explanation:
Using 1 N = 10^5 dyn and 1 m = 100 cm, 1 N m^−1 = 10^3 dyn m^−1 = 10 dyn cm^−1. Hence 0.072 N m^−1 = 0.72 dyn cm^−1.
6. The density of a material is 2.70 × 10^3 kg m^−3. Its value in g cm^−3 is:
A.
0.27 g cm^−3
B.
2.70 g cm^−3
C.
27.0 g cm^−3
D.
270 g cm^−3
Correct Answer:
2.70 g cm^−3
Explanation:
Since 1 kg = 10^3 g and 1 m^3 = 10^6 cm^3, 1 kg m^−3 = 10^−3 g cm^−3. Therefore 2.70 × 10^3 kg m^−3 = 2.70 g cm^−3.
7. A magnetic field of 3.5 × 10^−2 T is expressed in gauss as:
A.
3.5 G
B.
35 G
C.
350 G
D.
3500 G
Correct Answer:
350 G
Explanation:
The dimensional unit conversion is 1 T = 10^4 G. Thus 3.5 × 10^−2 T = 3.5 × 10^−2 × 10^4 G = 350 G.
8. A velocity of 72 km h^−1 is converted into cm s^−1. The result is:
A.
2.0 × 10^2 cm s^−1
B.
2.0 × 10^3 cm s^−1
C.
2.0 × 10^4 cm s^−1
D.
7.2 × 10^3 cm s^−1
Correct Answer:
2.0 × 10^3 cm s^−1
Explanation:
Using 1 km = 10^5 cm and 1 h = 3600 s, 72 km h^−1 = 72 × 10^5/3600 cm s^−1 = 2.0 × 10^3 cm s^−1.
9. The energy 1 eV is equal to 1.602 × 10^−19 J. Its value in erg is:
A.
1.602 × 10^−12 erg
B.
1.602 × 10^−19 erg
C.
1.602 × 10^−26 erg
D.
1.602 × 10^−2 erg
Correct Answer:
1.602 × 10^−12 erg
Explanation:
Since 1 J = 10^7 erg, 1 eV = 1.602 × 10^−19 × 10^7 erg = 1.602 × 10^−12 erg.
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