Physics Test - 5

CONCEPT:

The motion of Molecules:

• As we know that all molecules are in constant motion.
• Molecules of a liquid have more freedom of movement than those in a solid whereas molecules in a gas have the greatest degree of motion.

EXPLANATION:

• According to kinetic energy theory, if we increase the temperature of a gas, it will increase the average kinetic energy of the molecule, which will increase the motion of the molecules.
• This increased motion increases the outward pressure of the gas.
• The average kinetic energy of translation per molecules of the gas is related to temperature by the relationship:

Where E = kinetic energy, k_B = Boltzmann constant and T = temperature

• From the above equation, it is clear that the average kinetic energy of the gas molecule is directly proportional to the absolute temperature of the gas. 
• As the temperature of both gases is the same. Therefore, the average kinetic energy of O₂ and H₂ is the same. Hence, option 4 is correct.

The correct answer is option 2) i.e. 10-4 cm.

CONCEPT:

• Metric prefix: A metric prefix is a unit prefix placed before a basic unit of measurement. It represents the multiple of the unit in a convenient way. 

​A few common metric prefixes used are as below:

EXPLANATION:

One micron length = 1 micrometre = 1 μm = 1 × 10^-6 m

We know,

1 m →  100 cm

CONCEPT:

• Wave is a disturbance that transfers energy from one place to another.

The general expression for the SHM is given by:

Y = A Sin (ωt + θ)

Where A is the amplitude of the SHM, ω is the angular frequency, t is time and θ is the phase angle.

EXPLANATION:

Given that:

Y₁ = 15 sin (2πt + π/3)

So phase angle for this SHM = θ₁ = π/3

y₂ = 15 sin (2πt +π/4)

Phase angle for this SHM = θ2 = π/4

So phase difference = θ₁ – θ₂  = (π/3) – (π/4) = π/12

CONCEPT:

• Dimensional formula: It is a compound expression showing how and which of the fundamental quantities are involved in making that physical quantity.
• The dimension's principle of homogeneity says that an equation is dimensionally correct only if each term has the same dimension on both sides of the equation.

CALCULATION:

Given equation is x = at + bt²

The dimension of [x] will be equal to the dimension of [at] and [bt²]

[x] = [at]

[a] = [x/t]

x has dimension of length and t has dimension of time so unit of a will be ms^-1.

[x] = [bt²]

[b] = [x/t²]

x has dimension of length and t has dimension of time so unit of b will be ms-2.

So the correct answer is option 4.

CONCEPT:

Electric field intensity: 

• It is defined as the force experienced by a unit positive test charge in the electric field at any point.

Where E = electric field intensity, q_o = charge on the particle

EXPLANATION:

• The magnitude of electric force experienced by a charged particle in an electric field is given as,

• From the above equation, it is clear that the magnitude of electric force experienced by a charged particle in an electric field depends on the magnitude of the charge on the particle.
• Hence, option 1 is correct.

The correct answer is option 1 i.e. Force.

CONCEPT:

• Force: The interaction which after applying on a body changes or try to change the state of rest or state of motion is called force.
  • It is a vector quantity.

• Pressure: The force applied perpendicular to an object's surface on area of the region over which the force is spread is called force.
  • The SI unit of pressure is the pascal.
  • It is a scalar quantity because the pressure acts in all directions at a point inside a gas.

• Energy: The capacity to do work is called energy. 
  • It is a scalar quantity.

• Temperature: The measurement of hotness is called temperature.
  • It is a scalar quantity.
• Scalar quantities: The physical quantities which have only magnitude and no direction are called scalar quantities or scalars.
  • Examples: Mass, volume, density, time, temperature, electric current, Luminous, intensity, etc.
• Vector quantities: The physical quantities which have both magnitude and direction and obey the laws of 'vector addition' are called vector quantities or vectors.
  • Examples Displacement, velocity, acceleration, force, momentum, Impulse, etc.

EXPLANATION:​

From the above discussion we can say that;

• Only Force is a vector quantity in the given options. So option 1 is correct.

CONCEPT:

Electric Field Intensity:

• The electric field intensity at any point is the strength of the electric field at the point.
• It is defined as the force experienced by the unit positive charge placed at that point.

Where F = force and q_o = small test charge​

Electric dipole:

• When two equal and opposite charges are separated by a small distance then this combination of charges is called an electric dipole.
• The strength of an electric dipole is measured by a quantity known as a dipole moment i.e.

CONCEPT:

• Newton’s Second Law of Motion: The rate of change of linear momentum of a body is directly proportional to the external force applied on the body and this change takes place always in the direction of the applied force.
• According to the second law of motion, force

Where, K = constant of proportionality, p = momentum of the body, m = mass of the body, u = initial velocity of the body, v = final velocity of the body, and a = acceleration of the body.

EXPLANATION:

Given that:

momentum (p) = mt + n

According to the second law of motion, force

⇒ F = m + 0 = m = constant

• Since the force is always constant which is equal to m. So at time t = 1 second, the force will be equal to m.
• Therefore option 3 is correct.

CONCEPT:

• Capacitance: The capacitance tells that for a given voltage how much charge the device can store.

Q = CV

where Q is the charge in the capacitor, V is the voltage across the capacitor and C is the capacitance of it.

• And in the Series circuit, the reciprocal of the equivalent capacitance is the algebraic sum of all the reciprocal of the capacitance.

CONCEPT:

• Newton’s first law of motion: It is also called the law of inertia. Inertia is the ability of a body by virtue of which it opposes a change.
• According to Newton’s first law of motion, an object will remain at rest or in uniform motion in a straight line unless acted upon by an external force.
• The inertia of rest: When a body is in rest, it will remain at rest until we apply an external force to move it. This property is called inertia of rest.
• The inertia of motion: When a body is in a uniform motion, it will remain in motion until we apply an external force to stop it. This property is called inertia of motion.

EXPLANATION:

• When Ranveer pulled a table cloth from a table, at that time the dishes were at rest. Due to the inertia of rest, the dishes remain at rest because the cloths removed soon. Hence option 1 is correct.