2. Suppose a block is placed on a rough surface inclined relative to the horizontal and the coefficient of static friction between the block and the rough surface is μS. Let the incline angle be increased from θ = 0 until the block starts to move. What is the critical angle θ_c at which this slipping just occurs?
(A) θ_c= arctan(μ_S ) 
(B)θ_c= arccos(μ_S )
(C)θ_c=arcsin(μ_S ) 
(D)θ_c =π/2
(E) None of the above.

88. Which of the following endogenous DNA-damaging reactions occurs most frequently in cells? (A) depurination (B) ROS oxidation (C) methylation (D) deamination (E) depyrimidination

89. How many pairs in the following are TRUE?- Iron-sulfur protein– electron flow from FMNH2 to coenzyme Q- Coenzyme Q – lipid soluble electron carrier- Cytochrome c – accepts electrons from complex IV- Flavin mononucleotide – accepts electron from NADH in complex - Q cycle – funnels electrons from a 2-electron carrier to a 1-electron carrier- Catalase – converts reactive oxygen species into hydrogen peroxide- Proton-motive force – hydrolysis of ATP (A) 3 (B) 4 (C) 5 (D) 6 (E) 7

90. The coupling oxidative phosphorylation means the joint of two reactions including① glucose + ATP → pyruvate + ADP + Pi② NADH + 1/2 O2 + H+ → H2O + NAD+③ ADP + Pi + H+ → ATP + H2O④ oxaloacetate + NADH → NAD+ + malate + H+ (A) ①③ (B) ②③ (C) ①④ (D) ②④ (E) ③④

1. Which unit is not the SI (international system of units) derived unit? (A) dyne (B) watt (C) newton (D) volt (E) tesla

3. An escalator is used to move 20 people (60 kg each) per minute from the first floor of a department store to the second floor, 5 m above. The power required is approximately ______. (A) 100 W (B) 200 W (C) 1000 W (D) 2000 W (E) 4000 W

4. An air-bag company is designing a new product. The specification requires passengers of mass 75 kg to sit in a car traveling at 60 km/h. When the car hits the wall and stops there, the air-bag extends the stopping time up to 0.4 s. What is the average force on the passenger during this collision? (A) 408 N (B) 1680 N (C) 3125 N (D) 11259 N (E) 30625 N

5. The electric inductance L is defined as the magnetic flux ΦB divided by current I. What is the unit of the inductance L divided by electric resistance R ? (A) tesla (B) Hz (C) Wb (D) sec (E) None of the above.

6. A hydraulic press has one piston of diameter 2 cm and the other piston of diameter 8 cm. What force must be applied to the smaller piston to obtain a force of 1600 N at the larger piston? (A) 6 N (B) 25 N (C) 100 N (D) 400 N (E) 1600 N

7. The position of a particle is given by the expression x= 4 cos( 3 πt + π), where x is in meters and t is in seconds. What is the frequency? (A) 1.0 Hz (B) 1.5 Hz (C) 3.0 Hz (D) 4.0 Hz (E) 9.4 Hz

8. The average molecular translational kinetic energy of a gas molecule is ______. (The ideal gas constant is R. Boltzmann constant is kB. Temperature of gas is T.) (A) (3/2)kBT (B) (3/2)RT (C) (1/2)kBT (D) (1/2)RT (E) (n+3)kBT/2, where n is the number of internal degrees of freedom.