Physics MCQs
Physics Objective (Multiple Choice) General Knowledge & General Science Questions & Answers for SSC-CGL, UPPSC, NDA, CDS and all one day examinations of India.
31. Why a rubber ball rebounds but not a metal ball when both having the same mass, strike a wall normally with the same velocity?
[A] The rubber ball suffers greater change in momentum
[B] The metal ball suffers greater change in momentum
[C] Both suffer the same change in momentum
[D] The initial momentum of the rubber ball is greater than that of the metal ball
Show Answer
Correct Answer: A [The rubber ball suffers greater change in momentum]
Notes:
As per the question, the rubber ball rebounds while the metal ball does not. So if m and v be the mass and velocity respectively, the change in momentum of rubber ball = 2 mv (in magnitude) However, the change in momentum of the metal ball = mv The rubber ball suffers almost twice the change in momentum as experienced by the metal ball.
32. Wheelbarrow is a type of which class of lever?
[A] Class 1 Level
[B] Double Class 1 Lever
[C] Class 2 Lever
[D] Class 3 Lever
Show Answer
Correct Answer: C [Class 2 Lever ]
Notes:
The middle component determines whether the lever is 1st, 2nd or 3rd class. 1st class levers have fulcrum in the middle, for example, Teeter-totter, scissors and pliers. Out of them, scissors and pliers are considered a double Class 1 levers. In 2nd class levers, the load is in the middle. Examples of this are Wheelbarrow and Nut crackers. In class 3rd lever, the effort is in the middle. Examples are Tweezers, Stapler, Mousetrap etc.
33. A body moving in a circular path with a constant speed has a
[A] constant velocity
[B] constant acceleration
[C] constant kinetic energy
[D] constant displacement
Show Answer
Correct Answer: C [constant kinetic energy]
Notes:
In circular motion, the magnitude of the velocity of the body is constant but the direction is constantly changing. This means that, even though the speed is not changing, the velocity is changing. This means that body moving in a circular is accelerating. A body moving at constant speed in a circular path experiences an acceleration directed towards the centre of the circular path. Thus, kinetic energy remains constant because the speed is constant.
34. During _______ motion of an object along a straight line, the change in velocity of the object for any time interval is zero.
[A] linear
[B] translational
[C] equilibrium
[D] uniform
Show Answer
Correct Answer: D [uniform]
Notes:
During uniform motion of an object along a straight line, the velocity remains constant with time. In this case, the change in velocity of the object for any time interval is zero. This means, in the case of uniform motion, the rate of change of velocity, i. e. acceleration is equal to zero.
35. If the velocity of a body is doubled its momentum _______.
[A] remains same
[B] doubles
[C] becomes half
[D] becomes 4 times
Show Answer
Correct Answer: B [doubles]
Notes:
Momentum depends upon the variables mass and velocity. In terms of an equation, the momentum of an object is equal to the mass of the object times the velocity of the object. The momentum is directly proportional to an object’s mass and directly proportional to the object’s velocity. If the velocity of a body is doubled its momentum also doubles.
36. A solid needle placed horizontally on the surface of the water floats due to which of the following?
[A] capillary action
[B] water pressure
[C] surface tension of water
[D] viscosity of water
Show Answer
Correct Answer: C [surface tension of water]
Notes:
A solid needle placed gently & horizontally on the surface of water floats because of surface tension. It leads to the cohesive forces between water molecules to force the uppermost surface at the interface to act as a stretched membrame.
37. Hydro-electric power is a__:
[A] non-renewable natural resource
[B] a mixture of renewable and non-renewable natural resource
[C] neither renewable nor non renewable resource
[D] renewable natural resource
Show Answer
Correct Answer: D [renewable natural resource]
Notes:
Hydroelectric power is a source of renewable energy. The kinetic energy of water falling from dam is used for rotating the turbines to rotate the armateur in generator producing electricity.
38. Pressure Cooker cooks faster because__:
[A] boiling point decreases with rise of pressure
[B] it cooks the food at low pressure
[C] higher temperature is attained for cooking
[D] the material of the cooker is a good conductor
Show Answer
Correct Answer: C [higher temperature is attained for cooking]
Notes:
In pressure cooker as the name suggest, the developed high pressure raises the boiling point of water to about 120°C-140°C. This raised temperature not only speed up cooking but also proper cooking of foods cooked inside it.
39. Outside of cooking utensils are generally left black from below because__:
[A] it is difficult to clean daily.
[B] black surface is a good conductor of heat.
[C] black surface is a poor conductor of heat.
[D] black surface is a good absorber of heat.
Show Answer
Correct Answer: D [black surface is a good absorber of heat.]
Notes:
The outside surface of a utensil used for heating is coated black so that it may absorb more heat and make heating quicker. This is because black surface is both a good absorber and emitter of heat.
40. Which one among the following doesn’t have any effect on velocity of sound ?
[A] Pressure
[B] Temperature
[C] Humidity
[D] Density
Show Answer
Correct Answer: C [Humidity]
Notes:
The speed of sound varies depending on the temperature, pressure, and density of the medium through which the sound waves travel. In most of the cases, it is density which matters. Sound travels faster through denser air (or other material). The density of air is affected by atmospheric pressure, temperature, and altitude.
