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Motion - Exploration class 9   New NCERT 

Worksheet 2 Friction  A. Fill in the Blanks Friction always acts in the __________ direction to motion. The force of friction is greater between __________ surfaces. The irregularities on surfaces cause __________. __________ are used to reduce friction in machines. A __________ balance measures the force of friction. B. Conceptual Questions Why does a rolling object experience less friction than a sliding object? Why are shoes designed with grooves or tread patterns on their soles? What is the role of spring balance in studying friction? C. Think & Apply  A wooden block is pulled on a rough table and then on a smooth table. Predict and explain the difference in friction. Why do ball bearings reduce friction in machines? If friction didn’t exist, what challenges would we face in daily life? Think of at least three situations. D. Advantages and Disadvantages  List two situations where friction is helpful and two where it is not useful. Suggest two ways to reduce unwant...

Pressure in Liquids and Gases Worksheet 1 A. Fill in the Blanks Pressure in liquids __________ with depth. Liquids and gases are also known as __________. Gases exert pressure in __________ directions. Pressure is measured using an instrument called __________. The unit of pressure in the SI system is __________. B. Reasoning-Based Questions Why do deep-sea divers wear specially designed suits? Why do we not feel the atmospheric pressure around us? Why do aeroplanes have pressurised cabins for passengers safety while flying high in the atmosphere? Why are dams constructed thicker at the bottom than at the top? C. Diagram-Based Question Draw a diagram to show how pressure increases with depth in a liquid. In the diagram of a closed container, mark how gas pressure is exerted on all walls.

                                                                     FORCE & PRESSURE                                                                                   CLASS 8     Hints to answer the give reason type questions based on pressure class 8 Pressure in solids Check whether the area of contact is increasing or decreasing in given situation Write; Pressure is inversely proportional to area Write Increase or decrease in pressure according to the given area. Conclusion Pr...

PRACTICE WORKSHEET (CLASS - VIII) TOPIC – FORCE AND PRESSURE 1. When a force acts on a moving object, it can make the object a) move faster b) slow down c) stop d) all of these 2. Name the type of forces involved in the following :  a) A horse pulling a cart _________________________  b) A moving boat coming to rest when rowing is stopped ___________________ c) A coin falling to the ground on slipping from hand ______________________  d) A sticker attached to steel almirah without glue _________________________ 3. Two students fought over a lunch box, both started pulling it from opposite ends but the box didn't move from its place. What will you infer about the magnitude and direction of the forces? 4. An archer shoots an arrow in the air horizontally. However, after moving some distance, the arrow falls to the ground. Name the initial force that sets the arrow in motion. Explain why the arrow ultimately falls down. Assertion / Reason :  For question num...

 Worksheet-1 (Force and Pressure) Q.1.  Q.2.  Q.3. 

  Worksheet -3 

  Worksheet -2 

 Worksheet - 1 

  Body movements Q.1. What do you understand by the term ‘Movement’ and how is it different from the term ‘Locomotion’? Ans. A change in the position of an object is called ‘Movement’ like movement of hands while playing, doing exercise, blinking of eyes etc. The ability of living being to move its body from one place to another is called ‘Locomotion’ like living beings walk, run, crawl etc. Q.2. What are Joints and write a short note on each type of joint present in our body? Ans. Bones can not bend. We can bend and move our body only at some points where bones meet, such points are called joints. There are 4 types of joint present in our body: A ball and socket joint - this is the joint in which ball like surface of one bone is fitted into hollow space of another bone (also called socket). Such a joint allows movements in all directions. These can be found in shoulder joint, hip joint etc. A pivotal joint - this is the joint which allows rotation, twisting, extensio...

  SOUND Characteristics of sound Q.8. Define the following terms: Frequency, time-period and amplitude. Ans. Frequency : The number of oscillations per second is called the frequency of oscillation. Frequency is expressed in hertz. Its symbol is Hz. Time-period : The time period is  the time taken by the oscillating object to complete oscillation. It is expressed in seconds.   Amplitude : the amount of maximum displacement of vibrating particles of the medium from their mean position is called the Amplitude of oscillation. It is also known as size of vibration. The SI unit of amplitude is  the meter. Q.9. A pendulum oscillates 40 times in 4 seconds. Find its time period and frequency. Q.10. The sound from a mosquito is produced when it vibrates its wings at an average rate of 500 vibrations per second. What is the time period of the vibration? Q .11. How c an we differentiate sounds on the basis of their am...