Mechanics (Part – 4) - Mock Test 365

Total Questions: 38

21. The minimum work will be done when the body is_______. [S.S.C. Online MTS (T-I) 16.09.2017 (Shift-I)]

(a) a rope is pushed down from the plane
(b) raised vertically
(c) pushed on a smooth roller
(d) drawn on a flat horizontal surface

Correct Answer: (c) pushed on a smooth roller

Solution:Friction is less on a smooth surface. When friction is less, the force will be less on it and minimum work will also be done.

22. Rate of work done is _______ . [S.S.C. Online CHSL (T-I) 8.02.2017 (Shift-III)]

(a) Energy
(b) Power
(c) Momentum
(d) Impulse

Correct Answer: (b) Power

Solution:The rate of doing work is called 'power.'

P = w/t

where
w = work
P = power
t = time

23. What will be the effect when a ship enters a sea from a river? [C.P.O. S.I. 5.06.2016 (Shift-I)]

(a) It lowers
(b) It sways
(c) It rises a little
(d) It jolts

Correct Answer: (c) It rises a little

Solution:When a ship moves from a river to the sea, it will float higher. This is due to the difference in density between river water and seawater.

Density Difference:
Seawater contains dissolved salts, making it denser than freshwater found in rivers.
This increased density is the key factor.
Archimedes' Principle:
This principle states that the buoyant force on an object submerged in a fluid is equal to the weight of the fluid displaced by that object.
Effect of Higher Density:
Because seawater is denser, the ship needs to displace less of it to generate the same buoyant force required to support its weight.
Therefore, when the ship enters the sea, it displaces a smaller volume of water, causing it to rise higher in the water.

In simpler terms, the denser seawater provides more "lift," so the ship doesn't need to sink as deep to stay afloat.

24. In which form is the supplied heat energy stored during change in temperature of substance? [S.S.C. Online Graduation Level (T-I) 2.09.2016 (Shift-III)]

(a) Heat energy
(b) Kinetic energy
(c) Potential energy
(d) Both kinetic and potential energy

Correct Answer: (b) Kinetic energy

Solution:When heat energy is supplied to a substance and its temperature changes, that energy is primarily stored as:
Kinetic energy:

The heat energy causes the molecules of the substance to move faster.
This increased molecular motion translates to an increase in their kinetic energy.
Temperature is essentially a measure of the average kinetic energy of the molecules within a substance.
Therefore, the supplied heat energy is stored in the form of increased kinetic energy of the substance's molecules

25. Which of the following is an example of simple harmonic motion? [C.P.O. S.I. 6.06.2016 (Shift-l)]

(a) Earth spinning on its axis
(b) Simple pendulum motion
(c) Ball bouncing on the floor
(d) Motion of ceiling fan.

Correct Answer: (b) Simple pendulum motion

Solution:Simple harmonic motion (SHM) is a specific type of oscillatory motion where the restoring force is directly proportional to the displacement and acts in the opposite direction.

Key characteristics of SHM:

The motion is periodic.
There's a restoring force that pulls the object back towards its equilibrium position.
The acceleration of the object is proportional to its displacement.

26. A simple pendulum consists of a small metallic ball or a piece of stone suspended from a rigid stand by a thread. The metallic ball is called the________ of the pendulum. [S.S.C. Online MTS (T-I) 18.10.2021 (Shift-II)]

(a) knob
(b) bob
(c) hinge
(d) head

Correct Answer: (b) bob

Solution:A simple pendulum is made by tying a metal sphere to one end of a non-tightened thread. This small metal ball is called Bob.

The other end of the thread is tied to a hook in a stand so that the bob can oscillate.

27. For a wave, wavelength divided by the time period is equal to: [S.S.C. Online CGL (T-I) 13.08.2021 (Shift-III)]

(a) wave velocity
(b) amplitude
(c) phase difference
(d) frequency

Correct Answer: (a) wave velocity

Solution:Wavelength (λ): The distance between two successive crests or troughs of a wave.

Time period (T): The time taken for one complete wave cycle to pass a given point.

Wave speed (v): The speed at which the wave propagates.

The relationship between these quantities is given by the formula:

v=λ/T

Therefore, wavelength divided by the time period is equal to the wave speed.

28. The frequency of a wave is the reciprocal of its _______ . [S.S.C. JE Electrical Exam 24.03.2021 (Shift-II)]

(a) Speed
(b) Wavelength
(c) Time period
(d) Amplitude

Correct Answer: (c) Time period

Solution:The number of oscillations that an oscillating object stakes in one second is called its frequency.

It is represented by n.
The SI unit of frequency is Hertz or per second.
∴ Frequency (n)= 1/Time period (T)
Therefore, the frequency of a wave is equal to the inverse of the time period.

29. The 'to and fro' or 'back and forth' motion of an object is termed as: [S.S.C Online MTS (T-I) 26.10.2021 (Shin-II)]

(a) impulse
(b) vibration
(c) swing
(d) convulsion

Correct Answer: (b) vibration

Solution:The motion of an object known by the names "to and fro" or "back and forth' etc, in called vibration of harmonic motion.

30. Stress can be defined as the amount of_______. [C.P.O. S.I.6.06.2016 (Shift-I)]

(a) Scalar
(b) Tensor
(c) Phasor
(d) vector

Correct Answer: (b) Tensor

Solution:Stress is defined as resisting force per unit area of an element, on which load is applied.

Stress is always perpendicular to a cross-section in the element.
It is neither scalar (it cannot be numerically added), nor is it a vector (it does not follow the triangle rule of vector addition).
It is a tensor quantity because it describes things happening in two directions simultaneously.

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Mechanics (Part – 4)