# Competitive Exams: Physics MCQs (Practice_Test 12 of 35)

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- An elastic collision conserves
- kinetic energy but not momentum
- momentum but not kinetic energy
- neither momentum nor kinetic energy
- both kinetic energy and momentum

- Two planets A and B have the same material density. If the radius of A is twice that of B, then the ratio of the escape velocity VA/VB is
- 2
- -2
- 1/-2

- A satellite is moving in a circular orbit at a height of 100 km above the earth՚s surface. A person inside1he satellite feels weightless because
- acceleration due to gravity is almost zero at such a height
- the earth does not exert any force on the person
- the centripetal force makes the satellite move in circular orbit
- the forces due to the earth am the moon are almost compensated at such a height

- A rod length ‘l’ is inclined at an angle a with x-axis, An observer moving at a velocity V along the x-axis, will measure the angle of inclination as a (with g = 1/ ‘1’ V2/C 2) given by
- tan-1 tan a
- tan 1 g tan a
- tan 1 (tan a/g)
- tan-1 (g/tan a)

- Which one of the folk > wing is an example of steady and non-uniform flow?
- The flow of a liquid through a straight horizontal pipe at a constant rate
- The flow of a liquid through a straight horizontal pipe at a changing rate
- The flow of a liquid through a conical pipe at a constant rate
- The flow of a liquid through a conical pipe at a changing rate

- Water rises to a height h, in a capillary tube, when dipped in water. If the height of this capillary tube, above the water surface is less than h, then
- the water level will go down
- the water level will come to the top but the radius of curvature of the meniscus will increase
- the water level will come to the top but the radius of curvature of the meniscus will decrease
- the water will flow out of the capillary

- A soap bubble of radius r1 is blown at the end of a capillary tube of length L and radius R. If h is the viscosity of air and T is the surface tension of soap bubble. Then the time taken for the radius of the bubble to reduce to r2 due to flow of air through the capillary. Is equal to
- An oil drop of diameter 4 × 10 − 4 m falls through air. If the densities of oil and air are 900 kgm-3 and 1.293 kg m − 3 respectively and the coefficient of viscosity of air is 2.0 × 10 − 5 Nm-2s, then the terminal velocity of oil drop win be
- 0.2 × 10 − 4 m/s
- 2 × 10 − 4 m/s
- 4 × 10 − 4 m/s
- 8 × 10 − 4 m/s

- When a harmonic wave is propagating through a medium, the displacement ‘y’ of a particle of the medium is represented by y = 10 sin 2p/5 (1800t-x) . The time period will be
- sec
- sec
- 36 sec
- 360 sec

- Consider the mechanical vibrating systems shown in Figures A. B. C and D The vibrations are simple harmonic in:
- A and C
- A, B and C
- B and D
- A, B, C and D

- The displacement of a particle executing simple harmonic motion is given by y = 4 sin (2t + f) The period of oscillations is
- 2/p
- p/2
- p
- 2p

- If three tuning forks of frequencies 512,513 and 514 are sounded together simultaneously, then the number of beats per second is
- 0
- 1
- 2
- 3

- A particle of mass m describes an elliptical orbit: This motion can be shown to be the sum of two simple harmonic motions at rights angles to each other having
- the same frequency but different amplitudes
- the same frequency and the same amplitude
- different frequencies but the same amplitude
- different frequencies and different amplitudes

- Two sound waves of same amplitude can interfere destructively if
- their frequencies are equal and their phase difference is zero
- their frequencies are equal and their phase difference is 1800
- their phase difference is 900 irrespective of frequencies
- their phase difference is 1800 and their frequencies are unequal.

- Tuning fork A when sounded with tuning fork B of frequency 480 Hz gives 5 beats per second. When the prongs of A are loaded with wax, it gives 3 beats per second. The original frequency of A is
- 475 Hz
- 485 Hz
- 483 Hz
- 477 Hz