11th class ICS part 1 Physics Online Preparation

Define the following terms?

Position,

Uniforms

speed,

variable speed

average speed,

Instantaneous speed,

• Ans 1: Position:The location of an object relative to some reference point origin is known as position.
  Speed:The distance between covered by a moving body in one second is known as speed
  Speed = Distance covered /Time
  The speed is a scalar quantity. Its S.I unit is " m/sec" .
  Uniform Speed:A body is said to be moving with uniform speed, if it equal distance in equal intervals of time.
  Variable Speed:A body is said to be moving with variable speed if it covers unequal distance in equal intervals of time.
  Average Speed:The average speed of a moving body can be atained by dividing total distance covered by total time taken
  Instantaneous Speed:The speed of a body at any particular instant of time is known as instantaneous speed.

What is projectile motion? In what direction acceleration is zero in this motion?

• Ans 1: It is the two dimensional motion in which the object moves under constant acceleration due to gravity.
  The acceleration in horizontal direction is zero in projectile motion.

Add the mass given in kg up to appropriate precision: 2.189,0.089,11.8 and 5.32.

• Ans 1: As m= 2.189+0.089 +11.8+5.32+19.398 kg
  By appropriate precision m= 19.4kg

Define pressure of a gas.

• Ans 1: The pressure exerted by a gas is the momentum transferred to the walls of the container per sec unit area due to continuous collision of molecules of gas.

Define and explain supplementary units?

• Ans 1: The general conference on Weights and Measures has not yet classified certain unit of SI under either base or derived units. These SI units are called supplementary units.
  Radian and Steradian are supplementary units.
  Radian: The radian is the plane angle between two radii of a circle which cut off on the circumference an arc, equal I length to the radius. It is two dimensional angles.
  Steradian: The Sterdian is the solid angle subtended at the center of the sphere by an area of its surface equal to the square of radius of the sphere. It is three dimensional angles.

Explain briefly about residual heat of the earth.

• Ans 1: Hot igneous rocks within 10km of earth's surface are present in molten form They conduct heat energy from interior part of the earth. The temperature of these rocks is 200° C or more.

What do you mean by variable force?Give its two examples?

• Ans 1: The force which is not constant but varies in magnitude and direction or in both is called a variable force.
  
  1. Force a gravity acting on a rocket moving away from earth.
  2. Force exerted by the spring increases by the amount of stretch.

Show that 1 kWh = 3.6x10⁶J

• Ans 1: As
  1 kWh=1000 Wx 3600 s
  1 kWh =3600000 j
  1 kWh = 3.6x10⁶ j

Define Base and Derived Units.

• Ans 1: Base Unit: The unit that describe base quantities are called base units.
  Examples: Unit of length is meter and Unit of mass is kilogram.
• Ans 2: Derived Units: The units used to measure derived quantities are called derived units.
  Examples: Unit velocity is Meter per second (ms) Unit of acceleration is meter m3, Unit of force (Newton) N, Unit of presure is Pascal (Pa) Unit of charge Coulomb (C)

What is an Adiabatic process? Also give its two examples.

• Ans 1: Adiabatic Process:An adiabatic process is the process in which no heat is transferred to or from the system but the temperature of the system changes.
  Examples: Passage of sound through the air, rapid escape of air from a burst tyre and cloud formation etc.

A magnifying glass gives a five time enlarged image at a distance of 25 cm from the lens. What will be the focal length of the lens?

• Ans 1:

How many most common methods can be used for the conversion of biomass into fuel? Write their names.

• Ans 1: There are two methods for conversion of biomass into fuel:
  
  • Direct Combustion Method
  • Fermentation Method

Discuss the condition of equilibrium ?

• Ans 1:
  Newtons 1st Law of motion: This Law states that "A body at rest will remain at rest and a body in motion will continue its motion with uniform velocity unless it is acted upon by some unbalanced external force
  If F = 0 Then a = 0
  Explanation: The Ist law of motion is also known as law of inertia. The inertia is the property of a body which opposes any change in its state of motion or rest. Actually, when some force is applied on a body for changing its state of rest or uniform motion, then the body will affer resistance against this change. In the word, We can say that all the bodies try to maintain its state of rest or continue its uniform motion due to inertia. That is the why the newtons Ist law is also known as law of inertia.
  Examples:When we give a jerk to the branch of a tree, then the fruit falls down. It is because, when we give a jerk, the branch of the tree comes into motion suddenly.
  When a bus starts motion suddenly, the passengers experience a push in the back ward direction It is because, when the bus starts motion suddenly, the lower parts of the passenger in contact with the seats also come into motion. while the upper parts of the passengers are at remain at the rest In this attempt, they falls in the back words directions
  Newton's 2nd Law of motion:
  Statements: This law states that, "when a force is applied on a body, then acceleration is produced in the body in the direction of applied force and inversely proportional to the mass of the body.
  Explanation: The Ist Law of motion gives us the quantitative measurements of force, While the 2nd law of motion gives us the quantitative measurements of forces. now if the direction of motion of the body and direction of motion of the body and direction of forces are the same, then its velocity and acceleration increases. If the direction of motion of the body and direction of force are opposite in direction of force are opposite in direction, then the velocity and acceleration of the body will decreases gradually and finally become zero and the body will come to rest
  Example of newtons 2nd law of motion:
  
  When a body falls on a solid floor from the top of a building, the body experience or feel great pain. It is because, when the body falls on the floor, its acceleration become zero suddenly and the body faces huge force for very short period of time
  Newton,s 3rd Law of motion:
  This Law states that for every action, there is always a reaction. These forces are equal in magnitude but opposite in direction.
  Explanation: This law tells us that no body can experience a force from its surrounding, until this body exerts any force on its surrounding It means That forces are exerted in pairs.

Show that for the same initial speed and some range of projectile there are two mutually complementary angles of projection ?

• Ans 1:

Define Beat and beat frequency.

• Ans 1: Beat: Two waves of slightly different frequencies and travelling in the same direction produce beats.
  
  
  Beat Frequency: Number of beats per second is called beat frequency which is equal to the difference in frequencies.

• Ans 1:

Define base quantities and units.

• Ans 1: Base quantities: Base quantities are quantities on the basic of which other quantities are expressed.
• Ans 2: Examples: Length mass, time, electric current, temperature, intensity of light, amount of substance.
• Ans 3: Base Units: The units that decribe base quantities are called base units.
• Ans 4: Examples: Second ampere, kelvin, kilogram metre.

Two vectors have unequal magnitude. Can their sum be zero? Explain.

• Ans 1: No, the sum of two vectors having unequal magnitudes can't be zero. The sum of two vectors will be zero only when their magnitudes are equal and they act in opposite direction.

What is a machine ? Discuss the input and output and efficiency of a mechanical machine ?

• Ans 1: Machine:A machine is a thing or device with the help of which we can do more work than we can do by hands.
  Input of Mechanical machine:The amount of work dine on a machine by a given effort force is known as input of machine.
  Input = effort *effort arm
  Input = P*d
  Output of Mechanical Machine:The amount of work done by a machine on the load (weight) is known as output of the machine
  output = load * load arm
  output = w*d
  Efficiency:The ratio of output and input of a machine is known as efficiency
  Efficiency:Output / input
  n = w*d/ p*d

What are the problems having a high magnifying power in astronomical telescope?

• Ans 1: High magnifying power in astronomical telescope was accompanied by more spherical an chromatic aberration, geometric distortion and false colors.