Matric Part 1/9th Class Physics Chapter 2 Long Question With Answer for Unit 2 Kinematics

Question # 1

A cricket ball is hit vertically upwards and returns to ground 6s later. Calculate 1- maximum height reached by the ball. 2- Initial velocity of the ball. Given Data: t=6s =6/2 =3s h= ? Vi = ? Vf =0 g = -10ms-²

Ans 1: Solution: 2 Vf= Vi + gt Putting the values 0= Vi+(-10)(3) 0= Vi -30ms-¹ Vi=30ms-¹ 1 h= Vit + 1/2 gt² h=30(3) +1/2 (-10)(3)² = 90-90/4 = 90-45m h= 45m Ans'' ___

Question # 2

What are scalars and vectors. How vectors are represented

Ans 1: Scalers: physical quantities that can be described completely by its magnitude only are called as scaler quantity
Example: work, energy, mass, length, time and temperature etc
Ans 2: Vector; physical quantities that required both magnitude and direction for their representation are called vector quantities
Example: velocity, displacement , force , torque and momentum etc
Ans 3: Representation of vectors: Vectors can be represented by two way:
Symbolic representation, Graphical representation
Ans 4: Symbolic Representation: symbolically a Vectors can be represented in the following way
To differentiate a vector from scalar quantity we generally use bold letters to represent vector quantities such as F, a, d etc.
Ans 5: Graphical representation: Graphically a vector can be represented by a line segment with an arrow head.
length of line segment gives the magnitude of vector on selected scale
while the arrow head shows the direction of vector

Question # 3

Define and explain acceleration. also define uniform acceleration

Ans 1: Acceleration: acceleration is defined as the rate of change of velocity of a body. it is represent by a
Formula: Acceleration=change in velocity/time taken
acceleration= final velocity- initial velocity/time taken
a=vf-vi/t
Unit: its S.I unit is meter per second square. it is a vector quantity
Ans 2: Positive acceleration: Acceleration of body is positive if its velocity increase with time. The direction of positive acceleration is same in which body is moving without change in its direction
Ans 3: Negative acceleration: Acceleration of body is negative if its velocity decrease with time. The direction of negative acceleration is opposite to the direction in which body is moving. It is also known as deceleration or retardation.

Question # 4

Define the terms related to motion, position, distance, displacement

Ans 1: Position: the term position describes the location of place or point with respect to some reference point called origin
Ans 2: Distance: length of path between two points is called distance between those points
Unit: Distance is a scaler quantity. Its S.I unit is meter(m)
Ans 3: Displacement: the shortest distance between two points which has magnitude and direction is called displacement. It is represented by d
Unit: Displacement is a vector quantity and its S.I unit is meter

Question # 5

Describe uniform speed and uniform velocity

Ans 1: Uniform speed: a body has uniform speed if it covers equal distance in equal interval of time however short the interval may be
Ans 2: Uniform velocity: a body is said to be in uniform velocity if it covers equal displacement in equal interval of time however short the interval may be

Question # 6

what is graph. Explain the motion graphically

Ans 1: Graph: graph is a pictorial way or presenting information about the relation between various quantities. The quantities between which a graph is plotted are called variables
There are two types of variables
Independent variables, Dependent variable
independent variables: The quantity which vary independently called as independent variables e.g. Time
Dependent variables: The quantity which varies with independent quantity is called dependent variables e.g. Velocity
Ans 2: Distance time graph: in distance time graphs, time is taken at x axis and distance is taken on y axis

Object at rest: when distance covered by an object with time is zero with respect to observer and time is going on. Horizontal lines parallel to time axis on a distance time graph shows that object is at rest

Object moving with constant speed: speed of object is said to be constant if it covers equal distances in equal interval of time
Ans 3: Object moving with variable speed: when an object does not cover equal distance in equal intervals of time . In this case distance time graph is not a straight line.
Speed is higher when slope is greater. Speed is zero when slope is horizontal
Ans 4: Speed time graph: in speed time graph, time is taken along x axis and speed is taken along y axis

Object moving with constant speed: a straight line parallel to time axis represents constant speed of object
Object moving with uniform acceleration: straight line means that object is moving with uniform acceleration. Slope of line gives magnitude of its acceleration
Ans 5: Distance travelled by a moving object: area under speed time graph represents the distance travelled by object. If motion is uniform then area can b e calculated using appropriate formula for geometrical shapes represented by graph

Question # 7

Differentiate between distance and displacement.

Ans 1: Distance: Length of a path between two points is called the distance between those points. Explanation: Let S be the Length of the curved path between two points A and B on it. Then S is the distance between points A and B. Displacement: "Displacement is the shortest distance between two points which has magnitude and direction." Explanation: Consider a body that moves from Point A to point B along the curved path. Joint points A and B by a straight line. The straight line AB gives the distance which is the shortest between A and B. This shortest distanced in a particular direction is called displacement. It is a vector quantity and is represented by d.

Question # 8

Prove That S= Vit +1/2 at²

Ans 1: Second Equation of Motion: The total distance S travelled by the body is equal to the total area OABD under the graph. That is Total OACD+ triangle ABC) Area of OACD = OA x OD = Vi xt Area of ABC = 1/2 ( ACxBC) =1/2 (tx at) Since Total area = Area of rectangle OACD + OABD area of triangle ABC putting values in the above equation , we get S = Vit + 1/2 t x at S= Vit +1/2 at²

Question # 9

Explain the motion of freely falling bodies

Ans 1: Motion of freely falling bodies: Galileo was the first scientist to notice that all the freely falling objects have the same acceleration independent of their masses
Ans 2: Experiment: Galileo dropped various objects of different masses from the leaning tower of Pisa
Ans 3: Result: he found that all of them reach the ground at the same time
Ans 4: Gravitational Acceleration: The acceleration of freely falling bodies is called gravitational acceleration; It is denoted by g.
Value: on the surface of the earth, its value is approximately 10 ms-2
Ans 5: Sign significant: its value is positive when object move vertically downward. its value is negative when object move vertically upward

Question # 10

Define kinematics and explain rest and motion are relative

Ans 1: Kinematics: kinematics is the branch of mechanics which related to study of motion of objects without discussing the cause of its motion.
Ans 2: Rest: A body is said to be a t rest if it does not change its portion with respect to its surroundings
Ans 3: Motion; A body is said to be in motion if it changes its position with respect to its surroundings
Ans 4: Relative states of rest or motion: state of rest or motion of a body is relative
Example: A passenger sitting in moving bus is at rest because he is not changing his position w.r.t other passengers or objects in the bus. But to an observer outside the bus, the passengers and objects inside bus are in motion