Class 9 physics Chapter 1 notes national book foundation pdf

                          

Chapter #1

(physics –Class 9)

National Book Foundation

Comprehensive Questions (slo based solution )

 III. Give an extended response to the following questions .

1.     1.In a park , children are enjoying a ride on big wheel as shown . What kind of       motion the big wheel has and what kind of motion the riders have ?

     Ans/- The motion of wheel will be rotatory as it's moving about its axis . The motion of riders will be circular motion as they are moving in circular path .

2.   2.A boy moves for some time , give two situation in which his displacement is zero but covered distance is not zero ?

     Ans/- The displacement covered by object will be zero if the initial and final positions of object are same . 

    Example 1

     Consider a person is running around circular path . As in circular path intial and final positions are same . Although person has covered distance but it's displacement is Zero .

    Example 2 

    A person is moving in straight path suddenly he reurns back to it's initial position. As it's initial position became final as well  . In this case also distance has covered but displacement is Zero . 

 

3.  3.A stone tied to string is whirling in circle , what is direction of its velocity at any instant ?

    Ans/- The velocity will be tangent or perpendicular to centripetal force or radius of circle .

4. 4.Is it possible to acceleration object without speeding it up for slowing it down ?

   Ans /- Consider a stone tied to string is whirling in circle. After some time the stone will be moving with uniform velocity but velocity will change its direction with time . It's means the acceleration of stone will also be change.

   5.Can a car moving towards right have direction of acceleration towards left ?

    Ans/- Yes it's possible. 

   Explanation

     Consider a car is moving on straight path .The direction of acceleration and velocity both will towards right . But when driver apply brakes . Velocity will be decreased ,which result in deceleration. In this case velocity will be towards right but acceleration will be towards left .

    6 .With the help of daily life examples, tell the situations in which .

a) acceleration is in the direction of motion

Explanation

Consider a car moving on straight path . The direction of velocity and acceleration will be same .

 

b) acceleration is against the direction of motion

Explanation

When driver applies brakes the direction of velocity and acceleration will be opposite.

 

c) acceleration is zero and body is in motion

Ans/- yes , it's possible. 

Explanation 

Consider a body is moving with uniform velocity. As in this case initial and final velocity of body will be of same magnitude. So acceleration will be zero .

7  7 Examine distance-time graph of a motorcyclist ( as shown ) , what does this graph tell us about the speed of motorcyclist ? Plot the velocity-time graph for it ?

     Ans/- It represents that a body is moving with uniform velocity (10 m/s ) .

8. Which controls in the car can produce acceleration or deceleration in it ?

     Ans/-  Accelerator produces acceleration and brakes causes deceleration.

    9.  If two stones of 10kg and 1kg are dropped from a 1km high tower. Which will hit the ground with greater velocity ? Which will hit the ground first ? ( Neglect the air resistance )

    Ans/-  In the absence of air resistance both body will hit the ground at the same time with same velocity.

    10. A 1kg steel ball is dropped ( from rest ) and another is thrown downward with velocity of 5 m/s .which will have greater acceleration ? (Neglect the air resistance )

     Ans/-  In this case acceleration due gravity will 9.8 for both ball. As g is independent of their masses in the absence of air

R  Related Posts 

Chapter #2 (Numerical)
Chapter # 3 ( Numerical)

Chapter # 5 ( Numerical)

 

 F  FAQ 

1.What does speed look like on a graph?

In a Speed-time graph x-axis represents the time and y-axis represents the velocity. If the the line is horizontal parallel to x-axis . Then body is moving with uniform velocity . In that case acceleration of body is zero . 

2. Where is speed greatest on graph? 

Peak value of graph represents the greatest value . 

3.How do you tell if an object is speeding up or slowing down on a graph calculus?

y-axis represents the speed of object . You can easily determine the speed of object by examining the y-axis values . 

4.How is speed related to the distance travel?

AS average velocity or speed is distance covered by object in time t . So distance is directly related with velocity . If object cover greater distance its velocity will also increase . And if object covers less distance its velocity will also decrease . Because both quantities are directly related .

5.What does the distance time graph tell you?

You can easily determine the speed of object with time . With ease you can tell whether the object is moving with uniform , increasing or decreasing velocity .