Mock Test-3 (Paper-1) (Question 51-100)

Total Questions: 50

21. A ball is dropped from a satellite revolving around the earth at a height of 120 km. The ball will

Correct Answer: (b) continue to move with same speed along the original orbit of satellite

22. If a small raindrop falls through air

Correct Answer: (c) its velocity goes on increasing for sometime and then becomes constant
Solution:Velocity of raindrop increases until it reaches the terminal velocity

23. Why do two ice blocks join to form one block when pressed together?

Correct Answer: (a) Melting point of ice is lowered with increase in pressure
Solution:When two ice blocks are pressed together, little heat is generated due to pressure and of friction, which just melts the outer layer. Ehen that melts, friction decreases and dur to the low temperature of both the ice cubes, the water just refreezes.

24. An oil tanker is partially filled with oil and moves forward on a level road with uniform acceleration. The free surface of oil then

Correct Answer: (c) is inclined to the horizontal with larger depth at the rear end.
Solution:The two points in the same horizontal line do not have equal pressure if the liquid is accelerated horizontally with larger depth at rear end as the oil tanker is moving forward with uniform acceleration.

25. Which one of the following is the natural phenomenon based on which a simple periscope works?

Correct Answer: (d) Total internal reflection of light
Solution:Total internal reflection complete reflection of a ray of light within a medium such s water of glass from the surrounding surfaces back into the medium. The phenomenon occurs if the angle of incidence is greater than a certain limiting angle, called the critical angle.

26. The special technique used in ships to calculate the depth of ocean beds is

Correct Answer: (b) SONAR
Solution:SONAR or sound Navigation and Ranging is helpful for exploring and mapping the ocean because sound waves travel farther in the water than do radar and light waves. These also determine the time between the emission of sound pulse and its reception, the transducer can determine the range and orientation of the object.

While, LASER is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. Whereas, sonic boom is the sound associated with the shock waves created by an object travelling through the air faster than the speed of sound. On the other hand, reverberation is the prolongation of a sound.

27. Noise and music differ in their

Correct Answer: (c) note

28. Consider the following statements and select the correct code.

Assertion (A): Small glass beads fixed on traffic signals glow brightly when light falls upon them.

Reason (R): Light is totally reflected when the angle of incidence exceeds a certain critical value and light travelling in a denser medium is reflected from a rarer medium.

Correct Answer: (a) Both A and R are true and R is the correct explanation of A
Solution:Both of the statements are correct and statement 2 is also correct explanation for statement I. Total internal reflection is an optical phenomenon that happens when a ray of light strikes a medium boundary at an angle larger than a particular critical angle with respect to the normal to the surface.

If the refractive index is lower on the other side of the boundary, no light can pass through and all of the light is reflected. Thus because of this phenomena traffic light beads glow when light falls on them.

29. The colour of light is determined by its

Correct Answer: (a) amplitude
Solution:Light is made up of wavelength of light and each wavelength designates a particular colour. The colour of an object is the wavelengths of light that it reflects and colour we see is a result of which wavelengths are reflected back to our eyes.

30. Electric iron uses wires of alloy as

Correct Answer: (c) both (a) and (b)