phys promos

Question 1

progressive wave

Answer 1

transports energy from one point to another in the direction of wave propagation

Question 2

newtons 1st law

Answer 2

a body continues in its state of rest or uniform motion in a straight line unless a resultant external force acts on it (inertia)

Question 3

newtons 3rd law

Answer 3

if body a exerts a force on body b, body b will exert an equal and opposite force on body a (action reaction pair, must be different bodies, do not cancel, same type)

Question 4

mass

Answer 4

intrinsic property of a body which resists change in motion

Question 5

weight

Answer 5

force experienced by a mass in a gravitational field

Question 6

conditions for equilibrium

Answer 6

1. resultant force on body is zero
2. resultant torque on body about any axis is zero

Question 7

momentum

Answer 7

product of mass and velocity

Question 8

newtons 2nd law

Answer 8

rate of change of momentum is proportional to the resultant force acting on it and occurs in the direction of the force

Question 9

impulse

Answer 9

product of force acting on object and time for which force acts

Question 10

principle of conservation of momentum

Answer 10

when bodies in a system interact, the total momentum of the system remains constant, provided no net external force acts on it

Question 11

completely inelastic collsion

Answer 11

bodies stick together after collision, final velocity same, total momentum conserved, total ke not conserved

Question 12

principle of flotation

Answer 12

object floating in equilibrium, upthrust is equal in magnitude and opposite in direction to the weight of object/weight of fluid displaced

Question 13

principle of moments

Answer 13

for body in rotational equilibrium, sum of clockwise moments about any axis is the same as the sum of anticlockwise moments about the same axis

Question 14

couple

Answer 14

pair of equal and opposite forces whose line of action do not coincide

Question 15

centre of gravity

Answer 15

point at which the whole weight of the body appears to act

Question 16

angular displacement

Answer 16

angle the object makes with respect to a reference line

Question 17

angular velocity

Answer 17

rate of change of angular displacement with respect to time

Question 18

period

Answer 18

time taken for one complete oscillation

Question 19

frequency

Answer 19

number of complete oscillations per unit time

Question 20

object moving in uniform circular motion must experience a force

Answer 20

according to newtons first law, object will continue to move at its constant speed in the same direction unless there is a net force acting on it. hence must have a force acting on the object to constantly change its direction of motion

Question 21

why acceleration directed towards centre

Answer 21

object is moving at constant speed, no component of force (acceleration) in the direction of motion of object, otherwise will increase or decrease the speed of the object. thus direction of force has to be perpendicular to direction of motion

Question 22

simple harmonic motion

Answer 22

motion of a particle about a fixed point such that its acceleration is proportional to its displacement from the fixed point and is always directed towards the point

Question 23

angular frequency

Answer 23

rate of change of phase angle of oscillation and us equal to the product of 2 pi and its frequency

Question 24

damping

Answer 24

energy is removed from an oscillating system

Question 25

resonance

Answer 25

system responds at maximum amplitude to an external driving force. occurs when frequency of the driving force is equal to the natural frequency of the driving system

Question 26

transverse waves

Answer 26

particles oscillate in a direction perpendicular to the direction of energy transfer

Question 27

longitudinal waves

Answer 27

particles oscillate in a direction parallel to the direction of energy transfer

Question 28

polarisation

Answer 28

oscillations of the wave particles in transverse waves are restricted to one direction only and this direction is perpendicular to the direction of energy transfer

Question 29

malus law

Answer 29

intensity of beam of plane polarised light after passing through a plane polariser varies with the square of the cosine of the angle through which the polariser is rotated that gives maximum intensity

Question 30

principle of superposition

Answer 30

two or more waves of same kind meet at a point in space, resultant displacement at that point is equal to the vector sum of displacement of the individual waves at that point

Question 31

stationary wave

Answer 31

result of the superposition of the 2 progressive waves of the same type, freq, amplitude and speed, travelling along the same line but in opposite directions

Question 32

antinode and node

Answer 32

antinode point where amplitude is max node point where amplitude is zero

Question 33

diffraction

Answer 33

bending of waves after passing through an aperture or round an obstacle

Question 34

coherent

Answer 34

constant phase difference and same frequency

Question 35

interference

Answer 35

superposition of 2 or more waves to give a resultant wave whose resultant amplitude is given by the principle of superposition

Question 36

constructive and destructive

Answer 36

2 coherent waves arrive at same point with phase difference of zero to produce a maximum 2 coherent waves arrive at the same point with phase difference of pi rad to produce a minimum

Question 37

newtons law of gravitation

Answer 37

2 point masses attract each other with a force directly proportional to the product of their masses and inversely proportional to the square of the distance between them

Question 38

gravitational field

Answer 38

region of space in which a mass placed in that region experiences a gravitational force

Question 39

gravitational field strength

Answer 39

gravitational field strength at a point in space is the gravitational force experienced per unit mass at a point

Question 40

gravitational potential energy

Answer 40

work done by external force in bringing a mass from infinity to that point

Question 41

gravitational potential

Answer 41

work done per unit mass by an external force to bring a small test mass from infinity to that point

Question 42

why gravitational potential negative

Answer 42

gravitational force is attractive in nature. to bring a small test mass from infinity to a point, work done by external force is opposite to the direction of displacement of the mass. negative work done by external force thus negative

Question 43

escape velocity

Answer 43

minimum speed for the object to just escape from the gravitational influence of a massive body