Basic Physics

Question 1

A quantity that has only magnitude and no direction is called

Answer 1

Scalar quantity

Question 2

length, area, volume, mass, density, speed, work, energy

Answer 2

Are all scalar qty

Question 3

A quantity that has both magnitude and direction is called

Answer 3

vector quantity

Question 4

A quantity that has both magnitude and direction is called

Answer 4

vector quantity

Question 5

displacement, velocity, acceleration, force, momentum

Answer 5

Are all vector quantity

Question 6

The magnitude of the vector is shown by the ………..of the line and the direction of the arrow represents the direction

Answer 6

Length

Question 7

To find the resultant of two or more vectors

Answer 7

the triangle law, parallelogram law or polygon law is applied

Question 8

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

Answer 8

taken in the opposite order

Question 9

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

Answer 9

in magnitude and direction by the diagonal (AC) passing through that point

Question 10

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

Answer 10

closing side of a polygon (AF) taken in opposite order

Question 11

Speed

Answer 11

The rate at which a body is displaced in position is called its speed. Speed is a scalar qty

Question 12

Velocity

Answer 12

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.

Question 13

Acceleration

Answer 13

It is the rate of change of velocity. The change may be in speed or direction or both

Question 14

Mass

Answer 14

The mass of a body is the quantity of matter contained in it. Unit: kilogram (kg).

Question 15

Inertia

Answer 15

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.

Question 16

Force

Answer 16

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.

Question 17

Momentum

Answer 17

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.

Question 18

Laws of Motion.

Answer 18

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)

Question 19

Newton’s second law is equivalent to defining

Answer 19

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

Question 20

The expression on the left (F.δt) is known as the impulse of the force

Answer 20

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.

Question 21

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

Answer 21

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.

Question 22

The Law of Conservation of Momentum.

Answer 22

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.

Question 23

Work

Answer 23

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

Question 24

Power

Answer 24

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

Question 25

Newton’s Universal Law of Gravitation

Answer 25

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

Question 26

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

Answer 26

different, same

Question 27

Weight

Answer 27

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.

Question 28

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 ..........

Answer 28

weight,mass,eliminated

Question 29

Density

Answer 29

Density is the mass per unit volume of a substance. It is denoted by the symbol ρ.

Question 30

Pressure

Answer 30

Pressure is the force exerted per unit area. Unit: N/m2 or Pascals.

Question 31

Stress

Answer 31

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.

Question 32

Strain

Answer 32

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.

Question 33

Centripetal Force

Answer 33

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.

Question 34

Centrifugal Forc

Answer 34

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.

Question 35

Centrifugal Force is an ......... force and it exists only as an ............reaction to centripetal force.

Answer 35

inertia,equal and opposite

Question 36

When an ac is doing a loop the ......force remains constant however the......force keeps varying

Answer 36

Centripetal, centrifugal

Question 37

Angular velocity and acceleration are

Answer 37

vector quantities

Question 38

Angular momentum vector is represented by

Answer 38

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’.

Question 39

Centre of gravity

Answer 39

It is that point through which the weight of the body can be considered to act.

Question 40

moment of a force

Answer 40

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.

Question 41

Moment convention

Answer 41

The clockwise moments by convention are taken as positive while the anticlockwise moments are designated negative.

Answer 42

A system of two equal, unlike, parallel forces is called a couplecouple

Question 43

A couple can cause no motion in ......... but causes only ...........

Answer 43

translation,rotation