Test Prep Test Prep Certifications OAT Questions & Answers

• Question 241:

  An optical system has a focal length 30 cm away from the mirror, and an object 5 cm farther out from the focal point. What is the distance of the image formed in this concave mirror?

  A. 210 cm

  B. 250 cm

  C. 195 cm

  D. 300 cm

  E. 500 cm

  Correct Answer: A

  Di = Image distance

  Do = Object distance

  f = focal distance

  (1 / f) = (1 / Di) + (1 / Do)

  Rearrange to solve for Di: Di = (1 / f) - (1 / Do)

  (1 / Di) = (1 / 30) - (1 / 35)

  (1 / Di) = 1 / 0.0048

  Inverse both sides to get Di: ~210 cm.

• Question 242:

  A ray of light traveling in the air strikes water (n = 1.33). In which direction does the light bend?

  A. Towards the normal.

  B. Away from the normal.

  C. It will not bend.

  D. It depends on the angle of refraction.

  E. Need more information to solve this problem.

  Correct Answer: A

  Since light is going from a lower index of refraction (n) to a higher index of refraction, it will always bends towards the normal.

• Question 243:

  A 10 kg box is sitting on a frictionless inclined plane at an angle 10 degrees above the horizontal. What force must Mark apply to the box to prevent it from moving?

  A. 100sin10 N

  B. 10sin10 N

  C. 10sin100 N

  D. 100sin100 N

  E. Cannot be determined.

  Correct Answer: A

  The force Mark must apply to prevent the box from moving is mgsin.

  m = 10 kg g = 10 m/s2 (gravity) = 10 degrees

  Plugging these in gives: 10 ?10sin10, hence: 100sin10 N.

• Question 244:

  Diverging lenses always produce what type of image?

  A. Virtual

  B. Upright

  C. Smaller than the object

  D. All of the above

  E. None of the above

  Correct Answer: D

  All of these characteristics are indeed relevant to diverging lenses as the location of the object is irrelevant compared to converging lenses.

• Question 245:

  Maria leaves her house and drives to store 'A' for food, then to gas station 'B' and finally back to home. What was her total displacement?

  

  A. 0 miles

  B. 5 miles

  C. 12 miles

  D. 24 miles

  E. 27 miles

  Correct Answer: A

  Displacement is change of position from final to initial. Since Maria started at home and ended up at home, her total displacement was 0 miles. If the problem had asked what her distance traveled was, then one would expect it to be the perimeter, which is 12 miles.

• Question 246:

  If Kevin weighs 80 N on planet Earth, what will his weight be on the moon?

  A. The same

  B. He will weigh more on the moon

  C. He will weigh less on the moon

  D. Cannot be determined

  Correct Answer: C

  Weight = mass × gravity

  Kevin will have the same mass on Earth and the moon, but gravity on the moon is lower than the gravity on the Earth. Due to the correlation between weight and gravity, a lower gravity means a lower weight. Hence why Kevin will weigh less on the moon.

• Question 247:

  A spring is sitting in an equilibrium position. What would happen to the force of the spring if you pulled the spring to a length double of that of its equilibrium?

  A. Force would half

  B. Force would stay the same

  C. Force would double

  D. Force would quadruple

  E. Not enough information is provided

  Correct Answer: C

  F = -kx; where x = displacement from the equilibrium position Doubling the displacement (x) would double the force (F).

• Question 248:

  In the following circuit, identify the current going through I3.

  

  A. 1.25 A

  B. 2 A

  C. 2.5 A

  D. 5 A

  E. 10 A

  Correct Answer: C

  Begin by finding the total resistance of this circuit. Because this is a parallel circuit, total resistance is

  measured with the formula: 1/R = 1/R1 + 1/R2 etc.

  1/R = 1/8 + 1/8 + 1/4 = 1/2

  Thus, R = 2

  To find the current of I3, use the formula: I = V / R

  I = 10 / 4 = 2.5 A

  If one wanted to confirm their answer, they could find the currents of the other resistors and add up them.

  They should add up to the total current (I = V / R = 10 / 2 = 5 A).

• Question 249:

  An object is situated between the focal point and the concave mirror. Which of the following best describes the image produced?

  A. Real, inverted, smaller in size

  B. Virtual, upright, larger in size

  C. Real, inverted, larger in size

  D. Virtual, upright, smaller in size

  E. Real, inverted, no change in size

  Correct Answer: B

  It is very important to know the rules of image and object configuration for both concave and convex mirrors in regards to the focal point.

  The ray diagram below demonstrates the formation of the image from the object in the concave mirror. The image is upright, virtual ("behind" the mirror) and larger than the original object.

  

• Question 250:

  A woman is holding a 2 lb ball 3 feet above her head. How much work is the woman doing to keep the object above her head?

  A. 0 ft lb

  B. 3/2 ft lb

  C. 6 ft lb

  D. 12 ft lb

  E. Cannot be determined without more information.

  Correct Answer: A

  Given too much information when knowing the concept behind `work' is all that is needed to be solved.

  Because the ball is held above the woman's head and is not moving, the woman is not doing any work at all. There is no displacement, and thus, work amounts to 0.