Category: Class 11 Physics Objective Questions

Physics Multiple Choice Questions on “Introduction to Motion in a Straight Line”.

1. In which of the following states does a body possess kinetic energy?
a) Rest
b) Motion
c) When placed on a platform
d) In zero gravity
Answer: b
Clarification: The body moves in the state of motion. Hence it has a velocity and so kinetic energy. Kinetic energy = (1/2)mv².

2. Which of the following types of motion can be used for describing the motion of a car on a straight road?
a) Rectilinear
b) Circular
c) Periodic
d) Harmonic
Answer: a
Clarification: The motion of a car on straight road is happening along a straight line. Hence the motion can be called rectilinear as rectilinear motion happens along a straight line. Rest all are non rectilinear motions.

3. Which of the following types of motion cannot describe the motion of a clock’s hands?
a) Rectilinear
b) Circular
c) Periodic
d) Harmonic
Answer: a
Clarification: The hands of a clock move in a circular manner. Hence, the motion exhibited is circular motion. Moreover, it happens periodically, so it is also periodic motion. But its is not rectilinear motion.

4. Which force can possibly act on a body moving in a straight line?
a) Tangential force
b) Friction force
c) Centrifugal force
d) Centripetal force
Answer: b
Clarification: In the physical world, no surface is frictionless. Hence whenever a body moves, the force of friction acts on it. Rest all forces act on the body only when it moves along a curve and not along a straight line.

5. What kind of motion is rectilinear motion?
a) One dimensional
b) Two dimensional
c) Three dimensional
d) Zero dimensional
Answer: a
Clarification: Rectilinear motion happens along a straight line. A straight line is one dimensional. Hence, rectilinear motion is one dimensional.

6. When a body is in the state of complete rest, what kind of energy does it possess?
a) Potential energy
b) Kinetic energy
c) Total energy
d) Heat energy
Answer: a
Clarification: When the body is in the state of rest, there is no motion. Hence there is no kinetic energy, hence the total energy of the body is stored as its potential energy. The total energy is the sum of kinetic and potential energies.

7. Which of the following are obtained by dividing total displacement by total time taken?
a) Average velocity
b) Instantaneous velocity
c) Uniform velocity
d) Speed
Answer: a
Clarification: The average velocity is obtained by dividing total displacement by total time taken. Instantaneous velocity is calculated at an instant and not over a period of time. Speed is distance divided by time. Velocity is said to be uniform when velocity at every instant is equal to the average velocity.

8. What is the rate of change of rate of change of displacement of a body?
a) Velocity
b) Acceleration
c) Force
d) Jerk
Answer: b
Clarification: The rate of change of displacement of a body is velocity. The rate of change of rate of displacement of a body, or rate of change of velocity is acceleration.

Physics,

Physics Question Paper on “Various Forms of Energy : The Law of Conservation of Energy”.

1. Which of the following statements are true?
a) Energy can be created and destroyed
b) Energy cannot be created but only destroyed
c) Energy cannot be destroyed but only created
d) Energy can neither be created nor destroyed
Answer: d
Clarification: According to the law of conservation of energy, energy can neither be created nor destroyed but can only be changed from one form to another. This is also one of the fundamental concepts of thermodynamics.

2. The dimensions of energy are _____
a) [ML²T^-2]
b) [MLT^-2]
c) [ML²T^-1]
d) [MLT^-1]
Answer: a
Clarification: Energy = Force x Displacement
Units of energy = kg x (m/s²) x m
= kg x m² x s^-2
Therefore;
Dimensions of energy = [ML²T^-2].

3. Which of the following is not true?
a) Energy of an open system can be varied
b) Energy cannot be created
c) Energy cannot be destroyed
d) Energy cannot be transformed
Answer: d
Clarification: According to the law of conservation of energy, energy can neither be created nor destroyed but can only be changed from one form to another. Energy in an open system can be varying because of constant matter and radiation exchanges with the surrounding universe.

4. The law of conservation of energy is not applicable to mechanical systems as they require energy input to keep working.
a) True
b) False
Answer: b
Clarification: The law of conservation of energy is applicable to mechanical systems but it may not necessarily be applicable to a “machine” that requires constant power input to operate because it would then essentially be an open system.

5. The energy possessed by an object because of its motion is termed _____
a) potential energy
b) kinetic energy
c) nuclear energy
d) solar energy
Answer: b
Clarification: An object in motion possesses a velocity “v” at any instant of time.
This energy is termed “kinetic energy” and is given by;
Kinetic Energy = 1/2 x m x v²
where;
m = Mass of the object in motion

6. The maximum potential energy in a roller coaster is at _____
a) the top of the steep climb
b) somewhere during the climb
c) somewhere during the descent
d) the lowest point after the climb
Answer: a
Clarification: The potential energy is given by;
PE = m x g x h
where;
PE = Potential energy
m = Mass of the object
g = Acceleration due to gravity
h = Height of the object
Hence, the higher the object, the greater the potential energy.

7. Fire is a form of _____
a) solar energy
b) thermal energy
c) gravitational energy
d) kinetic energy
Answer: b
Clarification: Thermal energy is the consequence of the temperature of an object that is transferred in the form of heat from a source of greater temperature to a region or object of lower temperature by modes such as conduction, convection or radiation.

8. When a roller coaster is at the top of a steep hill, its potential energy is maximum. When it hurdles down the slope and comes to the bottom, the potential energy reduces greatly. Hence we can say that the law of conservation of energy is not valid here since energy is destroyed.
a) True
b) False
Answer: b
Clarification: When a roller coaster is at the top of a steep hill, its potential energy is maximum. When it hurdles down the slope and comes to the bottom, the potential energy reduces greatly. However, kinetic energy increases. Thus, there is a change from potential energy to kinetic energy and hence no destruction of energy.

9. When a person intakes 3000 kcal of food, he is able to do work requiring energy of 2500 kcal. This means that the human body destroys a fraction of energy obtained from food.
a) True
b) False
Answer: b
Clarification: If a person consumes 3000 kcal of food and does a work requiring 2500 kcal of energy, the rest of the 500 kcal is mostly used for the metabolic activities of the body and some are lost in the form of heat energy to the atmosphere.

10. For a freely falling body, which of the following quantities will not change?
a) Total kinetic energy
b) Total potential energy
c) Total mechanical energy
d) Insufficient data
Answer: c
Clarification: For a body falling freely under the influence of gravity, the velocity increases as heigh decreases. Hence, there is a reduction in potential energy but an increase in kinetic energy. However, the total mechanical energy, i.e., the sum of potential and kinetic energy always remains constant as per the law of conservation of energy.

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Physics Online Test for Class 11 on “Thermodynamics – Heat, Internal Energy and Work”.

1. Internal energy of a system is defined as?
a) The sum of kinetic energies of all molecules of the system
b) The sum of kinetic and potential energies of all molecules of the system
c) The sum of potential energies of the system
d) The average kinetic energy of all molecules
Answer: b
Clarification: The internal energy of a system corresponds to the energy possessed by all molecules. Thus it is the sum of kinetic and potential energies of all molecules in the system considered. Also note that potential energy is frame dependent, so we choose a frame in which the centre of mass is at rest.

2. Select the correct statement.
a) Internal energy is a path variable
b) Heat is a path variable
c) Work done is a state variable
d) Internal energy is a microscopic variable
Answer: b
Clarification: Internal energy corresponds to the mechanical energy of molecules. It is a state variable as it doesn’t depend on the path taken. While heat is the energy in transit, so it is a path variable. Internal energy is a thermodynamic variable and is therefore macroscopic as thermodynamics deals with bulk systems.

3. A box contains 10⁵ molecules. The average kinetic energy of each molecule is 0.5*10^-6J. With respect to an observer at rest the box, having a mass of 1kg, is moving with a velocity of 2m/s. What is the value of kinetic energy that will contribute to the internal energy?
a) 0.05J
b) 2.05J
c) 0
d) 2J
Answer: a
Clarification: When calculating internal energy of molecules, the system is to be studied from a frame in which the centre of mass is at rest. So the kinetic energy due to movement of the entire box will not be considered. Only the individual kinetic energies of molecules will be considered, and their value is: 10⁵*0.5*10^-6
= 0.05J.

4. If some heat is provided to a system and work is done on it, it is possible that internal energy will decrease. True or False?
a) True
b) False
Answer: b
Clarification: Internal energy corresponds to the mechanical energy of the molecules. When these molecules are provided with heat and are compressed their mechanical energy will increase. Both factors support the increase of internal energy hence the given statement is false.

5. Which of the following types of kinetic energies contribute to internal energy?
a) Translational
b) Rotational
c) Vibrational
d) Translational, Vibrational & Rotational
Answer: d
Clarification: Internal energy consists of the total kinetic energy of all molecules, which means all types, namely translational, rotational & vibrational kinetic energies contribute to internal energy.

6. A body has 15J of heat energy in a particular state. At the same state it has an internal energy of 30J. Assume no work is done, what will happen to the internal energy if 5J of heat is added to the system?
a) Heat energy = 20J, Internal energy = 35J
b) Heat energy = 15J, Internal energy = 30J
c) Heat energy = 15J, Internal energy = 35J
d) A body cannot have heat energy in a particular state
Answer: d
Clarification: Heat energy is the energy in transit. A system’s state cannot be defined by heat energy, it is defined by internal energy. Heat and work are path functions. Heat can be supplied or removed from a system but can’t define a system in a state.

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