FSc ICS Notes Physics XI Short Questions & Definitions Chapter 3 Motion and Force 1st Year Physics Notes Online Taleem Ilm Hub
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Dynamics: The branch of Mechanics which deals with the
motion of bodies under the influence of one or more forces.
Motion: Continuous change of location of a body with respect to its surroundings.
Linear motion: Motion in a straight line.
Translational motion ( or Rectilinear motion): A body moves with translational motion if each particle of the body undergoes the same displacement in a straight line in a given time.
Rotational motion: A body moves with rotational motion if each particle of the body moves in a circle about a straight line called the axis of rotation.
Vibratory motion: If the motion is back and forth over the same path about a mean position, it is called vibratory or oscillatory motion.
Rest: The position of the body with respect to its surroundings when it does not change.
Relative motion: The difference of two motions.
Relative velocity: The vector difference of the two velocities.
Trajectory: The path of a moving particle.
SR-71(reconnaissance jet): The Lockheed SR-71 Blackbird is the world’s fastest airplane. Originally designed for high-altitude military spy missions. Now used by NASA [National Aeronautical and Space Administration] for scientific research.
Falcon: Fighter-bombers aircraft. They are dual purpose aircraft that can drop bombs and also fight enemy planes. e.g. F-16 fighting Falcon.
Leopard: A large catlike beast of prey, with a beautiful spotted skin of yellow and black.
Cheetah: An animal of the cat family, resembling the leopard, found in Pakistan, Persia, India and Northern Africa, often tamed and trained to hunt gazelles.
Porpoise: Any of several small friendly whales from 5 to 8 feet long; commonly the dolphin.
Displacement: Distance moved from a reference point in certain direction.
Speed: i) The distance covered in unit time. ii) When a body moves, the rate of change of its position.
Velocity: The distance covered in unit time in a particular direction.
Acceleration: i) Rate of change of velocity. ii) Change of velocity in unit time.
Average speed: Total distance covered divided by total time.
Instantaneous Speed: The speed of a body in a particular instant.
Uniform Speed: If a body moves over equal distances in equal intervals of time, however small, it is said to move with uniform speed.
Variable Speed: When a body traverses unequal distances in equal intervals of time, it is said to move with variable speed.
Uniform Velocity ( or Constant Velocity ): If a body moves over equal distances in equal intervals of time, however small, in a particular direction, it is said to move with uniform velocity.
Variable Velocity: When a body traverses unequal distances in equal intervals of time, or when its direction of motion changes, it is said to move with a variable velocity.
Gradient: The degree of inclination of a slope. Mathematically, it is the ratio of vertical distance to horizontal distance.
Average Velocity: Total distance covered divided by total time taken in a particular direction.
Root mean square velocity: Square root of average of the square of molecular velocities.
Instantaneous Velocity: Velocity of a body in a particular instance. Symbolically it is defined as :
V = limΔt→ 0 ΔS/Δt
Average Acceleration: If the change in velocity of a moving body during the time interval Δt is ΔV , then the average acceleration is defined as :
a(av) = ΔV/Δt
Instantaneous Acceleration: The rate of change of velocity in a particular instant, symbolically,
a(inst) = limΔt → 0 ΔV/Δt
Uniform Acceleration: If the velocity increases by equal amounts in equal intervals of
time, it is said to be uniform acceleration.
Variable Acceleration: If the velocity increases by unequal amounts in equal intervals of time, it is said to be variable acceleration.
Deceleration ( or Retardation ): Rate of change of decrease of velocity; negative acceleration.
Wobble: To move unsteadily as a top (children’s toy) while rotating at a low speed.
First Law of Motion: A body continues its state of rest or uniform motion in a straight line unless it is compelled to change that state of motion by a force impressed upon it.
Inertia: i) The resistance of matter to any acceleration of its state of rest or motion. ii) The mass of the object is a quantitative measure of its inertia.
Second Law of Motion: The effect of an applied force on a body is to cause it to accelerate in the direction of the force. The acceleration is in direct proportion to the force and is inversely proportional to the mass of the body.
Third Law of Motion: To every action ( force ) there is always an equal and opposite reaction (force).
Impulse: The product of force and time for which it acts on a body.
Impulsive force: A large force but acts for a short time; it is time rate of change of momentum of a body.
Crumple: To press into wrinkles.
Skull: The bones forming the head and the face.
Cranium: The skull especially the bony part enclosing the brain.
Momentum: In a moving body, the product of its mass and velocity.
Linear momentum: In a body moving along a straight line, the product of its mass and linear velocity.
Isolated system: A system for which there is no transfer of mass and energy across the boundary.
Law of conservation of linear momentum: The total linear momentum of an isolated system remains constant.
Wind shield: Front transparent screen of a motor car.
Elastic collision: The collision in which the momentum and the kinetic energy of the system is conserved.
Inelastic collision: The collision in which the momentum of the system is conserved and not the kinetic energy.
Dimension: A measurement of any sort; especially length, height and width.
One dimension: A measurement which needs a single reference point; e.g. a point on a line.
Two dimensions: Measurement which needs two references; e.g. a point on a plane (x-y plane).
Three dimensions: Measurement which needs three references; e.g. a point in space (x-y-z coordinate system).
Four dimensions: Measurement which needs four reference; e.g. a point in space + time coordinates (relativistic frame of reference).
Missile: A thing thrown to injure another; a projectile.
Rocket: A missile or space vehicle powered by ejecting gas that carries both its own fuel and oxidant. They are independent of the earth’s atmosphere and are the power system used in space flights.
Chamber: An enclosed space, such as, of a rocket, containing the explosive chemicals.
Fuel: Inflammable material for supplying a fire or explosion.
Liquid oxygen: Condensed gaseous oxygen to a pale blue
liquid that is strongly magnetic.
Liquid hydrogen: Condensed gaseous hydrogen. It is colourless in small amounts but light blue in thick samples.
Propeller: Such thing which drives forward especially a device with blades for causing an airplane or a ship to progress.
Rocket propulsion: Rocket driving or pushing obtained from thrust of hot gases from engine exhaust.
Thrust: The forward reaction force of a jet or rocket engine.
Helicopter: A flying machine lifted and held up by horizontal propellers (rotating wings).
Aeroplane: An aircraft or flying machine, kept aloft by the reaction of motor-propelled planes upon the air also moves to wing borne flight.
Jet: Abbreviation for Joint European Torus.
Jet propulsion: Propulsion of aircraft or other vehicles in which one or more jets of hot gases are ejected at high speed from backwardly directed nozzles.
Rocket motion: The motion due to jet propulsion, i.e. due to thrust of hot gases from backwardly directed nozzles.
Aeroplane motion: The motion due to aeroplane’s wings designed to deflect the air and the propellers for causing the plane to move forward.
Helicopter motion: The motion due to the moving fans at the top of a helicopter.
Projectile motion: Projectile motion is two dimensional motion under constant acceleration due to gravity.
Projectile: i) An object launched in an arbitrary direction in space with the initial velocity having no mechanism of propulsion is called a projectile. ii) Any particle in the gravitational field of the earth, whose trajectory is assumed to be sufficiently short to consider the earth flat, and the effects of air resistance and the rotation of the earth are neglected.
Propulsion: A mechanism for driving forward with the mixture of fuel, engine or some shaft.
Simultaneously: Happening, done, or existing at the same time.
Trajectory: The path of a projectile.
Height of the projectile: The highest point a projectile attains during its flight.
Time of flight of projectile : The time taken by body to cover the distance from the place of its projection to the place where it hits the ground.
Range of the projectile: Maximum distance which a projectile covers in the horizontal direction.
Parabola: It is the locus of all points whose distance from a fixed point equals their distance from a fixed line.
Ellipse: A smooth oval curve as followed by planet Mars round the Sun.
Circle: It is the locus of points whose distance from a given fixed point (centre) is constant, (constant distance is called radius).
Ballistic: Of an instrument. Designed to measure an impact or brief flow of charge.
Ballistic motion: A motion in which a projectile is given an initial push and is then allowed to move freely due to inertia and under the action of gravity.
Ballistic missile: An un-powered and un-guided missile is called a ballistic missile.
Ghori Missile: On 25 May 2002, Pakistan marks the third successful test fire of surface-to- surface ballistic Ghori Missile with a range of 1,500 km and the Shaheen Missile with 800 km range. On May 28 1998, Pakistan successfully tested its nuclear capability.
Abdali: Short range domestically developed surface-to-surface missile having a range of 180 kilometers, and would be able to reach most border positions in India.
Ghaznavi: The missile capable of carrying warheads accurately up to a range of 290 km.
Aerodynamics: The study of the motion of gases (particularly air) and the motion and control of solid bodies in air.
Aerodynamic forces: Forces exerted upon a body when it moves in air, such as, air friction.
Parallel: Having a like course, lines lying in the same direction and being equidistant at all points from another.
Anti-parallel: Lines lying in the opposite direction and being equidistant all points from another line.
Plausible: Seeming to be true without necessary being so; having the appearance of truth.
Amoeba: A one-celled, microscopic animal found in ponds; one of the simplest forms of life.
Propel: To drive onward; push as a bicycle.
SLBM (Submarine launched ballistic missile): Ballistic missile submarines carry up to 24 SLBMs tipped with nuclear warheads. These missiles are stored in vertical launch tubes within the submarine, and can be launched while the sub is hidden underwater.
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