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Physics practise worksheet class 8
Political science (BA Honours)
University of Delhi
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DAV PUBLIC SCHOOL
JASOLA VIHAR NEW DELHI
PHYSICS PRACTISE ASSIGNMENT
CHAPTER-FORCE AND PRESSURE
- When happens when the two forces act in the opposite direction on an object?
- What is muscular force? Why it is called a contact force?
- Name some non-contact forces.
- What happens to pressure if contact area is doubled keeping thrust constant?
- We know that there is a huge amount of atmospheric pressure on us. But we do not feel it why?
- How will you relate force and pressure?
- What is the SI unit of force and pressure.?
- What is the effect on pressure if the surface area is increased or decreased?
- Differentiate between contact and non contact forces giving suitable examples.
- Why do dams have broad base?
- Show that liquid at a given depth exerts equal pressure in all the directions.
- The tip of a drawing pin has an area 1m 2. Find the pressure exerted if the force applied is 50 N.
- How is pressure in a liquid related to depth? Explain with the help of diagram.
CHAPTER-FRICTION
When pencil cell is released from certain point on an inclined wooden board, it travels a distance of 35cm on floor A before it comes to rest. When the same pencil cell is released from the same point on same inclined board, it travels a distance of 20cm on floor B before coming to rest. Which floor, A or B, offers grater friction? Give reason.
A car is moving towards North, What will be the direction of force of friction acting on this car due to surface of road?
You spill a bucket of soapy water on a marble floor accidently. Would it make easier or more difficult for you to walk on the floor? Why.
What kind of friction comes into play a) When a block of wood kept on table moves slowly? b) When block of wood kept on table just tends to move (or slip)? c) When block of wood kept on cylindrical iron road?
Explain why it is easier to drag a mat on floor when nobody is sitting on it but much more difficult to drag the same mat when a person is sitting on it.
What is the difference between static friction & sliding friction for a given pair of objects, which of the two is greater?
Explain why sole of our shoes wear out gradually?
What is meant by lubrication? Why it is important.
Why are car, aeroplanes & rockets streamlined?
Explain why a pencil will write on paper not in glass
When we try to push a heavy box kept on ground, it does not move at all. Which force is preventing this box to move forward? Where does this force act?
What is meant by streamlined shape? Name an object which usually has a streamlined shape
What is drag? Give an example.
CHAPTER-CHEMICAL EFFECTS OF ELECTRIC CURRENT
1.. The well cleaned two ends of the wire of a continuity tester, are dipped in a liquid that has been put in a clean beaker. From the following cases the bulb of the continuity tester would glow the brightest when the liquid in the beaker is a) Vegetable oil b) Acetic acid c) CuSO 4 d) Glycerine 2. Why does the electric conductivity of tap wter increases when common salt is added to it? 3. State any two prominent effects of the chemical reactions, taking place at the electrodes, when an electric current passes through an ionic solution. 4. It is known that an electric current can be induced in a metal wire coil by using magnet. How can a) this current be increased? b) this current be stopped? c) one reverse the direction of the flow of this current? 5. Write one difference between electroplating and electrorefining. 6. Name the anode and cathode of a voltaic cell. 7. Name the electrodes and the electrolyte used during electrolysis of water. Which gases are formed at the electrodes during this process? 8. a) Define electroplating and state any two of its applications. b) Explain with the help of a diagram how copper can be deposited on a zinc rod. 9. State the factors on which the process of electrolysis depends. 10. Kanav wants to remove the impurities from spoon given to him. a) Which application of electrolysis will be helpful for him? b) Explain the experimental set-up of the process. c) State any two reasons for coating ‘bicycle handles’ with chromium metal.
(c) laterally displaced and not dispersed. (d) reflected. 6. If light enters from water to air it bends __________ the normal 7.. A pencil dipped obliquely in water appears bent. Justify with the help of a diagram. 8. In a prism, the emergent ray is parallel to the incident ray. Is the given statement correct or not? Justify. 9. A transparent medium bends light by the same amount irrespective of the colour of light. True or false? 10. If an object is situated at the focal point of a convex lens, where is the image formed? 11. Which medium will bend light more−glass or water? Why? 12. A coin kept at the bottom of a glass bowl full of water appears to be higher than it actually is. With the help of a labelled diagram, explain why this happens. 13. 'As an object is slowly brought from infinity to the focus of a convex lens, the image travels from the focus to infinity.' Show this with the help of diagrams with five different positions of the object 14. Will a spectrum be formed if blue light falls on a prism? Give reasons.
What is the difference between the displacement produced by a rectangular glass slab in a ray of light and the deviation produced by a glass prism?
Define the following terms for a lens: (a) optical centre (b) principal axis (c) principal focus (d) focal length
Following questions consist of two statements – Assertion (A) and Reason (R). Answer these questions selecting the appropriate option given below: (a) Both A and R are true and R is the correct explanation of A. (b) Both A and R are true but R is not the correct explanation of A. (c) A is true but R is false. (d) A is false but R is true.
A. Assertion (A) : Light does not travel in the same direction in all the media. Reason (R) : The speed of light does not change as it enters from one transparent medium to another.
B. Assertion(A) : A ray of light travelling from a rarer medium to a denser medium slows down and bends away from the normal. When it travels from a denser medium to a rarer medium, it speeds up and bends towards the normal. Reason (R) : The speed of light is higher in a rarer medium than a denser medium..
C. Assertion(A) : Light travels faster in glass than in air. Reason (R) : Glass is denser than air.
D. Assertion(A) : Refractive index has no units. Reason (R) : The refractive index is a ratio of two similar quantities.
E. Assertion(A): Virtual images are always erect. Reason (R) : Virtual images are formed by diverging lenses only.
CHAPTER-THE HUMAN EYE
1 is the function of the ciliary muscles? 2. What kind of image is formed by eye-lens? 3. What are photoreceptors? 4. How we can see colours? 5. What is persistence of vision? 6. Which principle is used in cinematography? 7 happens when an object is brought closer to the eye and why? 8. What is the far point and near point of the human eye with normal vision? 9 What are the three defects of the eye? Explain each stating their cause, effect and correction. 10 developed Braille system? 11 Why in poor light we cannot perceive the true colours of an object? 12. Which is the most insensitive part of the eye retina?
CHAPTER-SOUND
- Define the term sound, frequency, time period, amplitude.
- Pendulum A makes 14 oscillations in 5 sec and pendulum makes 10 oscillations in three seconds. Which has a higher frequency? Express the frequency of each term in hertz.
- What is the range of audible frequencies for a normal human ear?
- Which type of voice is produced when the vocal cords are tight and thin?
- Which property of vibrations determines the pitch of the sound? Explain giving some examples.
- What is noise pollution? What are its major causes?
- What is the difference between noise and music?
- How does loudness of sound depends on amplitude?
- A pendulum oscillates 40 times in 4 sec. Find its time period and frequency?
- How is sound produced in – a. Humans b. Insects c. Birds
Physics practise worksheet class 8
Course: Political science (BA Honours)
University: University of Delhi
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