9th Class Physics Chapter 2 Exercise Short Questions with Answers
Q 2.2 : Explain translatory motion and give examples of various types of translatory motion .
Translatory Motion :
” The motion in which a body moves along a line (straight or curved ) without any rotation , is called translatory motion .”
Types of Translatory Motion :
- Circular motion
- Linear motion
- Random motion
1 . Circular Motion :
” The motion of an object in a circular path is known as circular motion .
Example : A car moving along a circular track .
2 . Linear Motion :
” Straight line motion of a body is known as linear motion .”
Example : Aero-plane flying straight in the air is linear motion .
3 . Random Motion :
” The disordered or irregular motion of an object is called random motion .”
Example :Motion of insects and birds is random motion .
Q 2.3 :Differentiate between the following .
|→A body is said to be at rest , if it does not change its position with respect to its surroundings .||→ A body is said to be in motion , if it changes its position with respect to its surroundings .|
|→A passenger sitting in a moving bus is at rest because he \ she is not changing his\her position with respect to other passengers or objects in the bus .||→To an observer outside the moving bus , the passenger and the other objects inside the bus are in motion .|
|Circular Motion||Rotatory Motion|
|→The motion of an object in a circular path is known as circular motion .||→The spinning motion of a body about its axis is called its rotatory motion .|
|→In circular motion , the point about which a body goes around is outside the body .||→In rotatory motion , the line around which a body moves about is passing through the body itself .|
|→Motion of earth around the sun .|
→A toy train moving in a circular track.
|→Motion of earth about its geographical axis .|
→Motion of top around its axis .
|Distance (S)||Displacement (d)|
|” Total length of a path between two points is called distance between these two points .”||“The shortest distance between two points is called displacement .”|
|→Distance is a scalar quantity .||→Displacement is a vector quantity.|
|Linear Motion||Random Motion|
|” Motion of a body along a straight line is called linear motion .”||” The disordered or irregular motion of an object is called random motion .”|
|Free falling object||Motion of gas molecules|
|“A scaler quantity is described completely by its magnitude .”||” A vector quantity is described completely by its magnitude and direction .”|
|Mass , Length , time , speed , volume , work , energy||Velocity , force , displacement , motion , torque|
Q 2.4 : Define the term speed , velocity and acceleration .
” The distance covered by an object in unit time is called its speed .”
Velocity (v) :
” The rate of change of displacement is called velocity .”
Acceleration (a) :
Q 2.5 : Can a body moving at a constant speed have acceleration .
Yes , A body moving at a constant speed have acceleration .
If a body is changing its direction then it has acceleration acting towards Centre provided by centripetal force .
Q 2.6 : How do riders in a Ferris wheel possess translatory motion but not rotatory motion ?
Riders in Ferris wheel have circular motion (a type of translatory motion ).
- Because their motion is in a circle without rotation .
- And the line about which wheel riders goes around , lies outside the body .
Q 2.7 : Sketch a distance-time graph for a body starting from rest . How will you determine the speed of a body from this graph ?
Q 2.8 : What would be the shape of a speed-time graph of a body moving with variable speed ?
The shape of velocity-time graph is zigzag i.e., not a straight line , when the body is moving with variable speed .
Q 2.9 : Which of the following can be obtained from speed-time graph of a body ?
i . Initial speed
ii . Final speed
iii . Distance covered
iv . Acceleration of motion
All the above quantities can be obtained from speed-time graph of a moving body .
Q 2.10 : How can vector quantities be represented graphically ?
Graphical representation of Vector :
Graphically , a vector can be represented by a line segment with an arrow head .
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Q 2.11 : Why vector quantities cannot be added and subtracted like scalar quantities ?
vector quantities cannot be added and subtracted like scalar quantities.
Reason : Vector quantities have direction and quantities having direction cannot be added and subtracted like scalar quantities .
Q 2.12 : How are vector quantities important to us in our daily life ?
Vector quantities are very important to us in our daily life .
- Vector quantities help us to determine position / direction of any place .
Example : Pilots use vectors to detect their destination .
Q 2.13 : Derive equations of motion for uniformly accelerated rectilinear motion .
Q 2.14 : sketch a velocity-time graph for the motion of the body . From the graph explaining each step , calculate total distance covered by the body .
- The area under a speed-time graph represents the distance travelled by the object (i.e. car ) .
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