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# MCQ in Physics Part 15 | ECE Board Exam

This is the Multiples Choice Questions Part 15 of the Series in Physics as one of the General Engineering and Applied Sciences (GEAS) topic. In Preparation for the ECE Board Exam make sure to expose yourself and familiarize in each and every questions compiled here taken from various sources including past Board Questions in General Engineering and Applied Sciences (GEAS), Physics Books, Journals and other Physics References

#### Continue Practice Exam Test Questions Part 15 of the Series

Choose the letter of the best answer in each questions.

701. What is the velocity of a wave along a cord having a linear mass of 4 g/cm if the cord is stretched to have a tension of 90 Kdyne?

a) 3600 m/s

b) 6300 m/s

c) 6030 m/s

d) 1460 m/s

Explanation:

702. What is the wavelength in air under standard conditions of a compressional wave whose frequency is 250 per second? Assume that the bulk modulus for air is 1.40 Mdyne/cm2 and the density of air is 1.29 g/L.

a) 132 cm

b) 231 cm

c) 123 cm

d) 321 cm

Explanation:

703. What tension would be required to create a standing wave with four segments in a string 100 cm long weighing 0.50 g. If it is attached to a vibrator with a frequency of 100 Hz?

a) 0.125 Mdyne

b) 0.521 Mdyne

c) 0.152 dyne

d) 0.251 dyne

Explanation:

704. What is the velocity of a wave along a chord having a linear mass of 4 g/cm if the chord is stretched to have a tension of 90 Kdyne?

a) 105 cm/s

b) 150 cm/s

c) 501 cm/s

d) 510 cm/s

Explanation:

705. What is the theoretical speed of sound in oxygen at 0ยฐC for a diatomic gas u = 1.40, and for oxygen M = 32.00 g/mol.

a) 315 m/s

b) 215 m/s

c) 500 m/s

d) 351 m/s

Explanation:

706. A sonar device on a submarine sends out a signal and receives an echo 5 seconds later. Assuming the speed of sound in water to be 1452 m/s, how far away is the object that is reflecting the signal?

a) 3526 m

b) 4215 m

c) 3625 m

d) 3512 m

Explanation:

707. What note is sounded by a siren having a disk with 16 holes and making 20 r/s?

a) 320 Hz

b) 220 Hz

c) 302 Hz

d) 230 Hz

Explanation:

708. If one sound is 5.0 dB higher than another, what is the ratio of their intensities?

a) 3.16

b) 31.6

c) 2.55

d) 35.1

Explanation:

709. Two sounds have intensities of 0.5 and 10 W/mยฒ respectively. How many decibels is one louder than the other?

a) 1.3 dB

b) 13 dB

c) 3.1 dB

d) 31 dB

Explanation:

710. Two sound waves have intensities of 100 and 400 โW/cm2, respectively. How much louder is one than the other?

a) 0.6 dB

b) 6 dB

c) 4 dB

d) 7 dB

Explanation:

711. If an unshaded electric lamp is 6 m above a table and is lowered to 3 m, how much has its luminance been increase?

a) 1

b) 2

c) 3

d) 4

Explanation:

712. A lamp produces a certain luminance on a screen situated 85 cm from it. On placing a glass plate between the lamp and the screen, the lamp must be moved 5 cm closer to the screen to produced same illuminance as before. What percent of the light is stopped by the glass?

a) 11%

b) 12%

c) 13 %

d) 14%

Explanation:

713. If a lamp provides an illuminance of 8.0 mc on a book is moved 1.5 times as far away , will the new illumination then be sufficient for comfortable reading?

a) 2.5 mc

b) 3.6 mc

c) 3 mc

d) 4 mc

Explanation:

714. If the light of a full moon is found to produce the same illuminance as a 1.0 cd source does at a distance of 4.0 ft., what is the effective luminous intensity of the moon? (The mean distance of the moon is 239,000 mi.)

a) 1.0 x 10 cd

b) 2.0 x 10 cd

c) 3.0 x 10 cd

d) 4.0 x 10 cd

Explanation:

715. An unknown lamped placed 6m from a photometer screen provides the same illumination as an 80 cd lamp placed 4 m from that same screen. What is the candle power of the unknown lamp?

a) 180 cd

b) 200 cd

c) 280 cd

d) 100 cd

Explanation:

716. A standard 48 – cd lamp is placed 30cm from a photometer screen and produces the same illumination as a 60 -cd lamped placed some distance away. How far away is the 60 -cd lamp from the screen?

a) 33.54 cm

b) 23.54 cm

c) 33.43 cm

d) 25.43 cm

Explanation:

717. Two point sources of light are placed 4.0m apart on a photometer. If one is a standard of 50 cd and they produced equal illuminance at a point 2.5m from the standard source, what is the intensity of the second source?

a) 18 cd

b) 19 cd

c) 20 cd

d) 17 cd

Explanation:

718. A point source of light of 10 cd is enclosed at the middle of a hollow sphere having a radius of 4 m. If an opening of 10 m2 exist in the sphere, what is the luminous flux through the opening?

a) 625 m

b) 62.5 m

c) 6.25 m

d) 0.625 m

Explanation:

719. Find the candle power of a point source of light that provides 20 mc of illumination on a surface 4 m away.

a) 320 cd

b) 32.0 cd

c) 3.20 cd

d) 217 cd

Explanation:

720. What is the vertical length of the smallest plane mirror in which a man 2 m tall can just see his full height from the top of his head to his feet?

a) 1 m

b) 2 m

c) 3 m

d) 4 m

Explanation:

721. A person backing a car up sees in the rearview mirror a person walking toward him at 5 km/hr. If the car is moving backward at 10km/hr., how fast does the person as viewed from the mirror approached the car.

a) 10 km/h

b) 20 km /h

c) 50 km/h

d) 30 km/h

Explanation:

722. The distance of comfortable distinct vision is about 25 cm for the average person. Where should a person hold a plane mirror in order to see himself conveniently?

a) 12.5 cm

b) 125 cm

c) 20 cm

d) 10 cm

Explanation:

723. An object is placed 20 cm in front of a concave mirror of radius 60 cm. Where is the image?

a) 12 cm

b) 25 cm

c) 60 cm

d) 100 cm

Explanation:

724. In what position in front of a spherical mirror should an object be placed to produce a real image which is magnified three times if the radius of curvature of the mirror is 18 cm?

a) 12 cm

b) 9 cm

c) 7 cm

d) 10 cm

Explanation:

725. A dentist holds a concave mirror of radius of curvature 6.0 cm at a distance 2.0 cm from a filling in a tooth. What is the magnification of the filling?

a) 2

b) 4

c) 5

d) 3

Explanation:

726. A convex mirror whose focal length is 15 cm has an object of 10 cm tall and 60 cm away. Find the position, nature, and size of the object.

For position:

a) -12 cm

b) -9 cm

c) -7 cm

d) -10 cm

Explanation:

727. For nature:

a) real

b) virtual

c) cannot be determined

d) none of these

Explanation:

728. For size:

a) 2 cm

b) 3 cm

c) 4 cm

d) 1 cm

Explanation:

729. In what position should an object be placed in front of a concave mirror having a focal length of 20 cm so that an erect image which is twice as large as the object is formed?

a) 12 cm

b) 9 cm

c) 7 cm

d) 10 cm

Explanation:

730. The angle of incidence of a ray of light at the surface of water is 40ยฐand the observe angle of refraction is 29ยฐ. Compute the index of refraction.

a) 13.25

b) 1.325

c) 1.25

d) 132.5 cm

Explanation:

731. The velocity of light in a liquid is 0.80 as fast as it is in air. What is the index of refraction of the liquid?

a) 13.25

b) 1.325

c) 1.25

d) 132.5

Explanation:

732. A ray of light strikes a water surface at an angle. The angle of refraction in the water is measured to be 22ยฐ. What must be the angle of incidence of the light ray have been?

a) 30ยฐ

b) 25ยฐ

c) 35ยฐ

d) 40ยฐ

Explanation:

733. What is the mass of a box which requires 3518 J of work to be pulled 9.36 m across a floor with a coefficient of kinetic friction between the box and the floor of 0.4?

a. 96 kg

b. 95.8 kg

c. 95.7 kg

d. 95.9 kg

Explanation:

734. How far must you pull a 10.9 kg box across the floor to do 123.3 J of work if the coefficient of kinetic friction between the box and the floor is 0.15?

a. 7.5 m

b. 7.6 m

c. 7.7 m

d. 7.8 m

Explanation:

735. How much work must be done to move a 3.8 kg chair 6.1 m across the floor at constant velocity if the coefficient of kinetic friction between the chair and the floor is 0.64 and you are pushing at an angle of 30.2ยฐ relative to the floor?

a. 231.5 J

b. 231.6 J

c. 231.7 J

d. 231.8 J

Explanation:

736. If you do 231.9 J of work to move a 19.8 kg chair 3.35 m across the floor at constant velocity, and you are pushing at an angle of 17.9ยฐ relative to the floor, what is the coefficient of kinetic friction between the floor and the chair?

a. 0.30

b. 0.31

c. 0.32

d. 0.33

Explanation:

737. A 80.4 kg diver jumps from a height of 2.64 m with an initial speed of 1.25 m/s. What is his speed entering the water?

a. 7.301 m/s

b. 7.302 m/s

c. 7.303 m/s

d. 7.304 m/s

Explanation:

#### Online Questions and Answers in Physics Series

Following is the list of practice exam test questions in this brand new series:

College Physics MCQs
PART 1: MCQ from Number 1 โ 50                        Answer key: PART 1
PART 2: MCQ from Number 51 โ 100                   Answer key: PART 2
PART 3: MCQ from Number 101 โ 150                 Answer key: PART 3
PART 4: MCQ from Number 151 โ 200                 Answer key: PART 4
PART 5: MCQ from Number 201 โ 250                 Answer key: PART 5
PART 6: MCQ from Number 251 โ 300                 Answer key: PART 6
PART 7: MCQ from Number 301 โ 350                 Answer key: PART 7
PART 8: MCQ from Number 351 โ 400                 Answer key: PART 8
PART 9: MCQ from Number 401 โ 450                 Answer key: PART 9
PART 10: MCQ from Number 451 โ 500                 Answer key: PART 10

Complete List of MCQs in General Engineering and Applied Science per topic

Series of MCQ in General Engineering and Applied Science

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