Basic Physics Flashcards
A quantity that has only magnitude and no direction is called
Scalar quantity
length, area, volume, mass, density, speed, work, energy
Are all scalar qty
A quantity that has both magnitude and direction is called
vector quantity
A quantity that has both magnitude and direction is called
vector quantity
displacement, velocity, acceleration, force, momentum
Are all vector quantity
The magnitude of the vector is shown by the ………..of the line and the direction of the arrow represents the direction
Length
To find the resultant of two or more vectors
the triangle law, parallelogram law or polygon law is applied
If two vectors (a & b) are represented in magnitude and direction by two sides of a triangle (BC & CA) taken in order, the resultant is represented by vector c in magnitude and direction by the third side of the triangle (BA) taken in the
taken in the opposite order
If two vectors are represented in magnitude and direction by the two adjacent sides of a parallelogram (AB & AD) drawn from a point, the resultant vector r is represented
in magnitude and direction by the diagonal (AC) passing through that point
If the vectors are represented by the sides of a polygon, taken in order, the resultant r is represented by the closing side of a polygon (AF) taken in opposite orde
closing side of a polygon (AF) taken in opposite order
Speed
The rate at which a body is displaced in position is called its speed. Speed is a scalar qty
Velocity
The rate of displacement of a body in a given direction is called its velocity. It is a vector quantity. Unit of both speed and velocity is m/s.
Acceleration
It is the rate of change of velocity. The change may be in speed or direction or both
Mass
The mass of a body is the quantity of matter contained in it. Unit: kilogram (kg).
Inertia
It is a property possessed by all bodies, which shows the reluctance to change their state of equilibrium. It is a quality and has no units. Inertia can be measured only in terms of mass, which is a scalar quantity.
Force
Application of force changes or tends to change the state of rest or uniform motion of a body in a straight line. In other words, force is that which changes or tends to change the momentum of a body. F = ma. Unit: Newton.
Momentum
The momentum of a body is the quantity of motion contained in a body and is the product of the mass and velocity of the body. Momentum is a vector quantity having the same direction as the velocity vector, and may be resolved into components, or combined with another momentum to give a resultant, like other vector quantities.
Laws of Motion.
First Law. Sir Issac Newton propounded three laws of motion: A body will continue in its state of rest or uniform motion in a straight line unless compelled to change that state by an external force. (b) Second Law. The rate of change of momentum is proportional to the applied force, and the change of momentum takes place in the direction of the applied force. (c) Third Law. Action and reaction are equal and opposite. (Note that action and reaction refer in this case to different bodies)
Newton’s second law is equivalent to defining
force as that which causes acceleration. From the second law we can say that F ∝ rate of change of momentum. But momentum = mv, and if m is constant for a given body, F ∝ m X rate of change of v, or F ∝ ma
The expression on the left (F.δt) is known as the impulse of the force
and is equal to the change of momentum caused by the force. Suppose a force F acts on a body of mass m for a short time t (e.g. when a bat strikes a ball), such that the velocity of the body changes from u to v. As F = ma, The acceleration ‘a’ produced by the force will be F/m. Substituting ‘a’ in v = u + at. v = u + F δt, m or F . δt = mv – mu.
Consider two bodies travelling in the same direction which collide with each other, the duration of the collision being a short time say δt. Throughout the collision each will experience a force
equal and opposite of that experienced by the other (Newton’s third law).The impulse of the force is F δ t and is the same for each body. Thus the change of momentum will be the same for each body. If at the time of collision, body A was overtaking body B, it is apparent that the effect of the impact will be to decrease the momentum of A and increase that of B, and the total momentum of the system of two bodies will remain unchanged.
The Law of Conservation of Momentum.
parts of a closed system are summarized in the law of conservation of momentum, which states that the total momentum in any given direction before impact is equal to the total momentum in that direction after impact.
Work
A force is said to do work on a body when it moves the body along its line of action. The amount of work done is equal to the product of the force and the distance moved (s) in the direction of the force. W = Fs. Unit: Nm or Joules
Power
The energy of a body is its capacity to do work. E = Fs. Unit: Joules.P = F s T = F v Where: Unit: Watts or Joules / second. 23. F s = = Force Distance the body has moved T = Time
Newton’s Universal Law of Gravitation
It states that any two bodies in the universe 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
This implies that different bodies at the same distance from the centre of the earth, having different masses will have correspondingly ……… forces of gravity acting upon them. However all of them will experience the …….. acceleration due to gravity, provided that only the force of gravity acts upon them
different, same
Weight
The force with which a body is attracted towards the centre of the earth is called its weight. It is equal to the product of mass and acceleration due to gravity at that point. W = mg, where g is the acceleration due to gravity at that point. Since g is not constant over the earth’s surface (more at poles and lesser at equator), therefore the weight of a body is variable, unlike its mass which remains constant.
A spring balance measures ……….. A see-saw type of balance or a steel yard or a weighbridge measures ……….. as in these cases force of gravity acts on both the sides and gets ……….
weight,mass,eliminated
Density
Density is the mass per unit volume of a substance. It is denoted by the symbol ρ.
Pressure
Pressure is the force exerted per unit area. Unit: N/m2 or Pascals.
Stress
Stress is the force exerted between two contacting bodies or parts of a body. It is measured as the force per unit area. Unit: N/m2.
Strain
Strain is the deformation caused by stress. It is recorded as the change of size over the original size. Since it is a ratio, it does not have any unit.
Centripetal Force
It was shown that a body travelling with uniform speed in a circle has an acceleration of v²/r towards the centre of the circle. The force producing this acceleration is termed as the centripetal force, and for a body of mass ‘m’ the centripetal force is mv²/r towards the centre of the circle.
Centrifugal Forc
It is the outward force on the body travelling along a curved path and represents the resistance of the mass to centripetal acceleration. Centrifugal Force is an inertia force and it exists only as an equal and opposite reaction to centripetal force.
Centrifugal Force is an ……… force and it exists only as an …………reaction to centripetal force.
inertia,equal and opposite
When an ac is doing a loop the ……force remains constant however the……force keeps varying
Centripetal, centrifugal
Angular velocity and acceleration are
vector quantities
Angular momentum vector is represented by
The vector length represents the magnitude of the quantity and it’s direction is perpendicular to the plane of rotation, i.e. parallel to the axis of rotation. The direction of the arrow is such that, on looking in its direction, the rotation is clockwise. The convention is known as the ‘right handed screw law’.
Centre of gravity
It is that point through which the weight of the body can be considered to act.
moment of a force
The moment of a force around a point is the product of the force and the perpendicular distance between that point and the line of action of the force.
Moment convention
The clockwise moments by convention are taken as positive while the anticlockwise moments are designated negative.
A system of two equal, unlike, parallel forces is called a couplecouple
A couple can cause no motion in ……… but causes only ………..
translation,rotation
